I had just been in a vehicle, then I get out at the mission zone. The mission is an assassination mission. I quickly find out I can't go into crouch mode. I check my controls. I select to rebind the crouch key, I find out the game is recognizing the keys I use to crouch as I can unbind the key and rebind it. I leave the game escape menu, and I still cannot crouch, I try to complete the mission anyway, and fail because I cannot hide in the bushes and was detected. After the "Failed" text on the screen, and the game reloaded, I could suddenly crouch again.
Not sure what happened. but the game flat out would not let my crouch. what a Weird annoying bug.