Subs delayed with 4k movies

[Mixzzz]

So I have run into an issue where subs are delayed with 4k movies. Doesn't matter if its x264 or x265, happens with both. Neither video or audio is being transcoded. Tried across multiple devices - samsung tv, android tv, android phone, windows app. However after opening the movies so many times between devices for testing at some point something changed and at least for 2 movies the subtitles got into sync. I am a little confused as to how that could've happend since I really didn't change any settings(I did try some options but reverted them back to original). If I force the bitrate down to so its starts transcoding, everything works as it should without delays from the first try.

Any solutions to this issue? Tried to search this issue but either the problem was slightly different or those fixes did nothing for me.

I have rarely had this issue with fhd movies which is most of my content.

[TheDreadPirate]

What kind of subtitles are they? And are they external subs or embedded?

[Mixzzz]

What kind of subtitles are they?  And are they external subs or embedded?

They were embedded Subrip ones. Tried external, same issue at first. Then subs get into sync with the movie. Except for one right now where embedded are ok but external are still delayed. I guess with this one the release might be bad.