Can't fast forward HEVC on LG TV

[flapjack]

Hi all
New to the forum but have been using Jellyfin for a little over a year now. Great app!  I have it running in a docker container in OMV on an old AMD based system.  I haven't had any issues at all until recently.

I've been ripping blurays to mkv and encoding them to either AV1 with 1080p content or now HEVC with 4K content.  I have an LG OLED65BXPUA with it's webOS that's maybe 3 years old now?
It doesn't like any 4K content in any codec other than HEVC (forces transcode otherwise).  
What's happening now is when I encode to HEVC on 4K movies that use Dolby Vision, I can't fast forward or chapter advance through.  The app on the TV just freezes and if I back out of the app the movies restarts from the beginning.  I've read in a few places that maybe the there's something wrong with the container (I've been using either mkv or mp4) but I don't get the problem on any other devices be they phones or computers.  Other forms of HDR seem to be ok so far on the TV.
Does anyone have any experience with a similar issue?  How did you get around it? 
Thanks!

[flapjack]

Just an update: I loaded the original mkv file into the jellyfin directory for one of the movies that's giving me an issue and it played fine on the TV. Was able to chapter advance and fast forward. I use handbrake to convert my files and haven't had a problem until now.