Hello,
didn’t found a thread about this bug here so I post one:
I absolutely LOVE this game, so do my old-clan-friends (it’s a bit like good old Wolf ET, only better in every way imo, setting, graphics, character-creation,… )…
But the so called “crouch-bug” is the most annoying thing at the moment in the game. I use slide/crouch&ironsight&move/run&slide again and so on permanently, and often suddenly, I have to jump to make smart and crouch/slide work again… often in bad situations… 
There are others who have the same problem, friends of mine and guys on the steam forum too (there is also explained how it can be easily reproduced):
http://forums.steampowered.com/forums/showthread.php?t=1888145&highlight=crouch
Don’t know if the devs are already aware of this, but is really annoying if you die because of this bug (especially when fighting human oppenents and not just bots of course). I hope there will be a fix for this soon…
Best Regards,
Dante