Re: Sprint bug
Ok so I finally found them:

It's hard to show a BUG where a command isn't processed because we can't show the buttons being pushed. However, as I stated before, double tapping the forward button (or double tapping up in the analog stick for consoles) automatically puts you in sprint mode, but when you're affected by the sprint BUG you enter this weird movement effect where you retrigger the beginning of the walking animation for each time you tap the forward button again. You can see I was "walking" (I was actually using the shift button to sprint to no avail), and then I started to tap the button and this visual effect took place.
I also managed to do this on another match:

In this same match I died and respawned as another character, and the BUG persisted:

Unfortunately I didn't find any recording of this BUG persisting between matches, but I remember this was a thing. As this is a very rare BUG, at least to me, I have no idea what triggers it, nor any method to stop the BUG from affecting you.