Same problem on Chromecast with Google TV (Android 12, July 2022), Plex Android 9.15.0.38159: subtitle styling works perfectly for the same file when I choose supported audio track and it’s broken when I choose audio track that needs transcoding. I agree I have seen that error for quite a while on multiple versions of Android app (also on MiBox).
[EDIT:] It’s broken for both external and embedded in MKV SRT subtitles whenever audio is transcoded.
