Misidentifying Season 1 AoT as Season 2 AoT

[CrookiesAndCash]

I'm having a really weird issue where Jellyfin (half?) identifies the first season of Attack on Titan as the second season. 

To get the basic details out of the way first, all relevant library settings are

Prefer embedded titles over filenames - OFF
prefer embedded episode information over filenames - OFF

Metadata downloaders (TV Shows)
- AniDB
- AniList
- AniSearch
- TheTVDB
- Missing Episode Fetcher 

Metadata downloaders (Seasons)
- AniDB
- TheTVDB

Metadata downloaders (Episodes)
- AniDB
- TheTVDB

Metadata savers - NFO

Automatically merge series that are spread across multiple folders - ON

And my folder structure is 
--- Attack on Titan (2013)
------ Season 01
--------- Attack On Titan S1E1.mkv
--------- Attack On Titan S1E2.mkv
--------- Attack On Titan S1E3.mkv
--------- ...

If there is anything else possibly relevant I'll try to provide it. 

Now onto describing the actual issue though, the episode titles and descriptions for all of Season 1's content appear to be taken from Season 2. Every other season looks fine at a first glance, it's JUST season 1 that's broken. Weirder still, if I click on Season 1, some of the information is correct. For instance the top title will say "Attack on Titan Season 2" but the subtitle under it will say "Season 1". BUUUT if I click on the hyperlinked text for that top title, it ACTUALLY takes me to Season 2 - for some reason.

Extra strangely, if I click on the 3 dots under Season 1 and click 'edit metadata', all of the identifiers say Season 1! Nothing anywhere in the metadata says that it should be showing as Season 2!