Weapon switch desync
A common trick in Doom is to switch to a weapon (usually the fist) right before picking up a stronger weapon, in a way that the said weapon is loaded up and ready to fire in much less time. The issue starts when one switches weapons and picks up the weapon at roughly the same time (the weapon switching occurring right after the weapon pickup, I believe). The client performs the trick nonetheless, however, this trick did not happen server-side, so as soon as one shoots the weapon, the server will forcefully snap the client's weapon to the fist, as it has always been in the server. Here is another description of what happens:
<HeX9109-> the server thinks the fist is out because the signal to switch to fist got to the server as zakken was picking up the ssg
<HeX9109-> so the client switches to the ssg, but the server is in the middle of "switching the weapon" and puts up the fist
<HeX9109-> so client gets ssg and server gets fist, but when zakken fires the server is like WOAH I THOUGHT YOU HAD THE FIST OUT WHAT THE FUK
The attached demo showcases the bug quite a few times. This may not happen to players with low ping, seeing as I haven't noticed any others actively pointing this bug out.
Happens to me always with high ping. This probably never happens to me with low ping. So there must be some packet loss issue or something. Also when i play with high ping this happens to me really very rarely. I use this method all time but i dont change on fist i use next weapon on my mouse3.
I did mention the fist, but the bug happens with any other weapon: for example, if one switches to the pistol while picking up a strong weapon, they end up firing the pistol instead of a fist, and so on.
Multiplayer Weapon Desync Demo