Hi everyone!
Problem
I’m struggling the past couple of days after the update to 10.6.0 with my Jellyfin. My iOS devices do not transcode anymore! (I did not test Android, but different web browsers on different PCs, Macs work fine and transcode.
My server runs on a Windows 10 machine and I stalked the forums and Reddit over the past week to hope to find someone with the same issue, but without success.
Here is the thing. After the update, I noticed that my JellyfinApp (iPhone6, 12.4.5) did not work with all my videos anymore. I tested my iPad and had the same issue. I cant transcode anything anymore via the Jellyfin App or via the website.
The log talks about an unknown profile that requests to watch something and I guess this is the issue. (A log is at the end of this post)
I found on GitHub someone with the same problem (I guess, at least the bug report matches 100%) but they did not found any solution yet. https://github.com/jellyfin/jellyfin/issues/2546
What did I try?
First I checked for FFmpeg, relinked it in the app, installed the latest version, and linked that but nothing worked.
Then I did a fresh install of Jellyfin for windows but kept the program data. - did not work
Then I did a fresh install of Jellyfin for windows and deleted every reference of it from the machine. - no success.
Help
Does anyone have an idea of how to overcome this problem? A dirty solution for now? I tried to install infuse, but it seems to need a subscription to work 
Log
[2020-07-26 21:13:57.159 +02:00] [INF] [33] Emby.Server.Implementations.HttpServer.HttpListenerHost: WS "::ffff:91.5.184.97" request
[2020-07-26 21:13:57.646 +02:00] [WRN] [22] Emby.Server.Implementations.HttpServer.HttpListenerHost: HTTP Response 200 to "127.0.0.1". Time (slow): 0:00:00.5185534. "thisisnotalink.localhost:8090/System/ActivityLog/Entries?startIndex=0&limit=7&minDate=2020-07-25T19%3A13%3A57.122Z&hasUserId=true"
[2020-07-26 21:13:57.779 +02:00] [WRN] [19] Emby.Server.Implementations.HttpServer.HttpListenerHost: HTTP Response 200 to "127.0.0.1". Time (slow): 0:00:00.6500363. "thisisnotalink.localhost:8090/System/ActivityLog/Entries?startIndex=0&limit=7&minDate=2020-07-25T19%3A13%3A57.123Z&hasUserId=true"
[2020-07-26 21:14:00.397 +02:00] [ERR] [22] Emby.Server.Implementations.HttpServer.HttpListenerHost: Error processing request: "The process cannot access the file 'C:\ProgramData\Jellyfin\Server\cache\images\resized-images\9\975b7361-8bb9-eee9-7a7d-aac2024883be.jpg' because it is being used by another process". URL: "thisisnotalink/Items/22bc1c6c2bf01dc2362cd47443398d7b/Images/Backdrop/0?tag=6666b80fa2b60abe244eaacaf767dd78&maxWidth=2560&quality=80"
[2020-07-26 21:14:08.405 +02:00] [INF] [10] MediaBrowser.Api.Playback.MediaInfoService: GetPostedPlaybackInfo profile: DeviceProfile { Name: null, Id: null, Identification: null, FriendlyName: null, Manufacturer: null, ManufacturerUrl: null, ModelName: null, ModelDescription: null, ModelNumber: null, ModelUrl: null, SerialNumber: null, EnableAlbumArtInDidl: False, EnableSingleAlbumArtLimit: False, EnableSingleSubtitleLimit: False, SupportedMediaTypes: "Audio,Photo,Video", UserId: null, AlbumArtPn: null, MaxAlbumArtWidth: 0, MaxAlbumArtHeight: 0, MaxIconWidth: null, MaxIconHeight: null, MaxStreamingBitrate: 120000000, MaxStaticBitrate: 100000000, MusicStreamingTranscodingBitrate: 192000, MaxStaticMusicBitrate: null, SonyAggregationFlags: null, ProtocolInfo: null, TimelineOffsetSeconds: 0, RequiresPlainVideoItems: False, RequiresPlainFolders: False, EnableMSMediaReceiverRegistrar: False, IgnoreTranscodeByteRangeRequests: False, XmlRootAttributes: [], DirectPlayProfiles: [DirectPlayProfile { Container: "mp4,m4v", AudioCodec: "ac3,eac3,mp3,aac,dca,dts,flac", VideoCodec: "h264,vc1", Type: Video }, DirectPlayProfile { Container: "mp3", AudioCodec: "mp3", VideoCodec: null, Type: Audio }, DirectPlayProfile { Container: "aac", AudioCodec: null, VideoCodec: null, Type: Audio }, DirectPlayProfile { Container: "m4a,m4b", AudioCodec: "aac", VideoCodec: null, Type: Audio }, DirectPlayProfile { Container: "flac", AudioCodec: null, VideoCodec: null, Type: Audio }, DirectPlayProfile { Container: "alac", AudioCodec: null, VideoCodec: null, Type: Audio }, DirectPlayProfile { Container: "m4a,m4b", AudioCodec: "alac", VideoCodec: null, Type: Audio }, DirectPlayProfile { Container: "wav", AudioCodec: null, VideoCodec: null, Type: Audio }], TranscodingProfiles: [TranscodingProfile { Container: "aac", Type: Audio, VideoCodec: null, AudioCodec: "aac", Protocol: "hls", EstimateContentLength: False, EnableMpegtsM2TsMode: False, TranscodeSeekInfo: Auto, CopyTimestamps: False, Context: Streaming, EnableSubtitlesInManifest: False, MaxAudioChannels: "2", MinSegments: 2, SegmentLength: 0, BreakOnNonKeyFrames: True }, TranscodingProfile { Container: "aac", Type: Audio, VideoCodec: null, AudioCodec: "aac", Protocol: "http", EstimateContentLength: False, EnableMpegtsM2TsMode: False, TranscodeSeekInfo: Auto, CopyTimestamps: False, Context: Streaming, EnableSubtitlesInManifest: False, MaxAudioChannels: "2", MinSegments: 0, SegmentLength: 0, BreakOnNonKeyFrames: False }, TranscodingProfile { Container: "mp3", Type: Audio, VideoCodec: null, AudioCodec: "mp3", Protocol: "http", EstimateContentLength: False, EnableMpegtsM2TsMode: False, TranscodeSeekInfo: Auto, CopyTimestamps: False, Context: Streaming, EnableSubtitlesInManifest: False, MaxAudioChannels: "2", MinSegments: 0, SegmentLength: 0, BreakOnNonKeyFrames: False }, TranscodingProfile { Container: "wav", Type: Audio, VideoCodec: null, AudioCodec: "wav", Protocol: "http", EstimateContentLength: False, EnableMpegtsM2TsMode: False, TranscodeSeekInfo: Auto, CopyTimestamps: False, Context: Streaming, EnableSubtitlesInManifest: False, MaxAudioChannels: "2", MinSegments: 0, SegmentLength: 0, BreakOnNonKeyFrames: False }, TranscodingProfile { Container: "mp3", Type: Audio, VideoCodec: null, AudioCodec: "mp3", Protocol: "http", EstimateContentLength: False, EnableMpegtsM2TsMode: False, TranscodeSeekInfo: Auto, CopyTimestamps: False, Context: Static, EnableSubtitlesInManifest: False, MaxAudioChannels: "2", MinSegments: 0, SegmentLength: 0, BreakOnNonKeyFrames: False }, TranscodingProfile { Container: "aac", Type: Audio, VideoCodec: null, AudioCodec: "aac", Protocol: "http", EstimateContentLength: False, EnableMpegtsM2TsMode: False, TranscodeSeekInfo: Auto, CopyTimestamps: False, Context: Static, EnableSubtitlesInManifest: False, MaxAudioChannels: "2", MinSegments: 0, SegmentLength: 0, BreakOnNonKeyFrames: False }, TranscodingProfile { Container: "wav", Type: Audio, VideoCodec: null, AudioCodec: "wav", Protocol: "http", EstimateContentLength: False, EnableMpegtsM2TsMode: False, TranscodeSeekInfo: Auto, CopyTimestamps: False, Context: Static, EnableSubtitlesInManifest: False, MaxAudioChannels: "2", MinSegments: 0, SegmentLength: 0, BreakOnNonKeyFrames: False }, TranscodingProfile { Container: "ts", Type: Video, VideoCodec: "h264", AudioCodec: "ac3,eac3,mp3,aac", Protocol: "hls", EstimateContentLength: False, EnableMpegtsM2TsMode: False, TranscodeSeekInfo: Auto, CopyTimestamps: False, Context: Streaming, EnableSubtitlesInManifest: False, MaxAudioChannels: "2", MinSegments: 2, SegmentLength: 0, BreakOnNonKeyFrames: True }, TranscodingProfile { Container: "mp4", Type: Video, VideoCodec: "h264", AudioCodec: "ac3,eac3,mp3,aac,dca,dts,flac", Protocol: "http", EstimateContentLength: False, EnableMpegtsM2TsMode: False, TranscodeSeekInfo: Auto, CopyTimestamps: False, Context: Static, EnableSubtitlesInManifest: False, MaxAudioChannels: null, MinSegments: 0, SegmentLength: 0, BreakOnNonKeyFrames: False }], ContainerProfiles: [], CodecProfiles: [CodecProfile { Type: Video, Conditions: [ProfileCondition { Condition: NotEquals, Property: IsAnamorphic, Value: "true", IsRequired: False }, ProfileCondition { Condition: EqualsAny, Property: VideoProfile, Value: "high|main|baseline|constrained baseline", IsRequired: False }, ProfileCondition { Condition: LessThanEqual, Property: VideoLevel, Value: "51", IsRequired: False }, ProfileCondition { Condition: NotEquals, Property: IsInterlaced, Value: "true", IsRequired: False }], ApplyConditions: [], Codec: "h264", Container: null }], ResponseProfiles: [ResponseProfile { Container: "m4v", AudioCodec: null, VideoCodec: null, Type: Video, OrgPn: null, MimeType: "video/mp4", Conditions: [] }], SubtitleProfiles: [SubtitleProfile { Format: "vtt", Method: External, DidlMode: null, Language: null, Container: null }] }
[2020-07-26 21:14:08.516 +02:00] [INF] [10] MediaBrowser.Api.Playback.MediaInfoService: User policy for "Bloham". EnablePlaybackRemuxing: True EnableVideoPlaybackTranscoding: True EnableAudioPlaybackTranscoding: True
[2020-07-26 21:14:08.518 +02:00] [INF] [10] MediaBrowser.Api.Playback.MediaInfoService: Not eligible for DirectPlay due to unsupported subtitles
[2020-07-26 21:14:08.519 +02:00] [INF] [10] MediaBrowser.Api.Playback.MediaInfoService: Not eligible for DirectStream due to unsupported subtitles
[2020-07-26 21:14:08.520 +02:00] [INF] [10] MediaBrowser.Api.Playback.MediaInfoService: Profile: "Unknown Profile", Path: "F:\Series\Family\Season 1\Family.S01E01.x265.AC3.MultiSUB-Family1.mp4", isEligibleForDirectPlay: False, isEligibleForDirectStream: False
[2020-07-26 21:14:08.522 +02:00] [INF] [10] MediaBrowser.Api.Playback.MediaInfoService: Not eligible for DirectPlay due to unsupported subtitles
[2020-07-26 21:14:08.523 +02:00] [INF] [10] MediaBrowser.Api.Playback.MediaInfoService: Not eligible for DirectStream due to unsupported subtitles
[2020-07-26 21:14:08.524 +02:00] [INF] [10] MediaBrowser.Api.Playback.MediaInfoService: Profile: "Unknown Profile", Path: "F:\Series\Family\Season 1\Family.S01E01.x265.AC3.MultiSUB-Family1.mp4", isEligibleForDirectPlay: False, isEligibleForDirectStream: False
[2020-07-26 21:14:08.525 +02:00] [INF] [10] MediaBrowser.Api.Playback.MediaInfoService: Not eligible for DirectPlay due to unsupported subtitles
[2020-07-26 21:14:08.526 +02:00] [INF] [10] MediaBrowser.Api.Playback.MediaInfoService: Not eligible for DirectStream due to unsupported subtitles
[2020-07-26 21:14:08.527 +02:00] [INF] [10] MediaBrowser.Api.Playback.MediaInfoService: Profile: "Unknown Profile", Path: "F:\Series\Family\Season 1\Family.S01E01.x265.AC3.MultiSUB-Family1.mp4", isEligibleForDirectPlay: False, isEligibleForDirectStream: False