Bro I found a solution to this problem
I just went to the Facebook app, then force stopped the app, and then cleared both the cache and data.
As a result I got logged out of my account and had trouble signing back in but when I was able to sign in again and started watching videos and reels the lag was gone!
Try this bro and get back to me if it worked for you as well!
Merry Christmas 🎄 🎁 God bless!