I have merged movie versions in Jellyfin (4K Remux + 1080p transcode). When I pick the 1080p in Infuse’s version picker, the 4K gets streamed instead. Verified by checking Jellyfin’s open file
descriptors on the server; the 1080p file is never read.
Turns out the Jellyfin API returns MediaSources sorted by resolution (highest first), and if the client doesn’t explicitly pass the correct MediaSourceId to the stream endpoint, the server
defaults to the highest one. Swiftfin had the same bug and already fixed it: