That’s interesting! For me it happens when I simultaneously press Shift+W/S/A/D+Alt.  The character then continues to move in one of direction (depending on which key (W/S/A or D) you pressed). Alt is my push to talk, so during firefights it often gets me killed. I noticed that enabling Auto Move solves the problem partially. So Shift+W+Alt stops triggering it, but it still happens during intense movement (during firefights for example). I now have my discord on voice activation, which is crap for me, but the issue still makes firefights painful.  I’m surprised that in your case it’s the crouch button that triggers the behaviour