Issue with Mouse jitter

[That2rb2DUDE]

I figured out that when holding 2-3 buttons or just the tab button alone for some reason triggers the mouse jitter.

Been having this problem with SDL2 for awhile now and its pretty annoying when your just want to cruise through a single player or play multiplayer in general.

 

[~Confusion~]

I second this. The jittering seems to be still there even when I'm not holding any buttons, but if I do, then it gets really awful...

 

[Monster Iestyn]

Hey, I know this is over a year old now, but is this basically the same issue as that in https://mb.srb2.org/showthread.php?t=42848 ? Or related to, at least?

Either way, if the test exe fixes these issues anyway, then I can mark this as fixed.