Phone is visibly stuttering

Jul 16, 2018

For last few weeks I had this random problem with my Mi5. It suddenly started lagging like hell. For example it takes few seconds for it to wake up the screen after clicking the button. The animations are stuttering and even is sound (you can actually hear the stutter when someone is calling).

I already wiped everything clean (just saved about 20 apps with Titanium Backup) and reflashed MIUI but the problem persist.

MIUI 10 8.7.12 (but it was the same on MIUI 9)

Could it be a battery issue? I have really no idea what to do with it.