I’ve run into that sometimes when I seek (rewind or fast-forward).  It will be all frozen, but the clock will still be counting as if it’s playing.  It’s a weird bug that I wish would get fixed.  But, sometimes, I’ve found I can fix it by pressing the left arrow to seek back by 10 seconds.
 
Otherwise, if you’re just having slow streams, you should get a Real-Debrid subscription.