subtitles not in sync with videos in mobile app of jellyfin

[Sujal Sharma]

And what kind of subtitles are they?  ASS?  SRT?  PGS?

I'm assuming ASS subs.

Also, on your phone, are you using the web player or the integrated player?

Settings > Client settings

Yes they are ASS subs

 I don't know what kind of player it is but I was using official jellyfin app from play store, the videos were being played on it