maybe your frames are dropping since there is so much going on at once?

I think the problem is that you're running into the other Scout and it's messing up your/his hitbox. My brother does it to me in mge on purpose so I can't turn to the side and shoot him.

Nah not about fps, happens simply always when 2 scouts interact.

This sounds somewhat logical, I wonder if this kind of hitbox thing could be fixed, like with cylinder hitboxes or something like that?

This happens to me when im playing with high ping

definitely a ping thing. should really avoid getting close to people when u have high ping

I have this problem always with even 20-30 ping.

This is how hitboxes in TF2 interact. If you walk into someone and get inside their hitbox, you'll be pushed out so the hitboxes don't overlap. It's most noticable on scout because you can get into their hitbox quickly before the game realises due to the fast movement speed. You can actually use this to your advantage on scout on low ping by tapping w when you're at very close range next to someone to repeatedly jitter out of them. Because it's you that's being displaced it makes your model really jittery and hard to hit, although this is mostly impractical in actual games.

The interaction does change with ping though. I think because the game takes more time to realise you're inside someone you can actually get through the middle of them and you'll get pushed out in a different direction which is why you can sort of slide through other players on scout at higher ping. You can't use this to your advantage too well because you kind of get teleported randomly and aren't looking in the direction of the player when you come out the other side.

Does it use that fixed orientation bounding box for those calculations?

Yeah pretty sure collision hulls are what calculate this so it's wider on the diagonals etc. You can kind of test it by wing into a player standing still and strafing and seeing how you slide around them.
I have no proof the game actually does this, but I think it's logically how they'd stop people from getting stuck inside each other. It just comes from having to play really gay with movement on scout when I was on a shitty jittery laptop and couldn't aim. People accused me of ratehacking a lot. The main problem with doing this is that any decent scout will kill you before you get into the ridiculously close range you need to do this.

This is a good example of it https://www.youtube.com/watch?v=1wGcNzFd3as

I don't think the issue here is actually the shape of the hitbox though, the jittering in and out would still occur if the collision hull shape was changed because that's the only way I can think of stopping players getting stuck inside each other. Changing the bounding box to be a smaller cylinder would also probably make hitting projectiles a lot harder and scouts even better than they are already. I'm not sure I'd want valve to fuck with that.

Yeah okay this makes more sense now, my main point was really to find out whether this is a problem on my end allowing anyone else to outplay me for dumb reasons, or simply something touching everyone, thanks.