video fps drops

[OnurAkbas]

while watching downloaded videos sometimes fps goes down to 15 or less checked video in pc and video is stable, if watching longer videos than 30 minutes video app just stuck. is there any solution for this?
tried different video apps
tried lots of videos
8.12.20
mi5x

 

[Kappe]

Try updating ti 8.12.27

 

[OnurAkbas]

Try updating ti 8.12.27

updated to 9.1.3 but same

 

[OnurAkbas]

now vlc is working correctly but mi video still has problem