• Pick up a one-handed melee weapon (machete or hammer)
• Move the melee weapon from the gear the the hands, or assign it to a quick slot menu and click it
• Press "stand up" key (default "C")
• From standing position: Raise the fist with your meele in the right hand (default key "Space Bar")
• Try to attack (fire button). All should works fine till now.
• Press "crouch" button (Default "X"). The character WILL NOT REACT.
• Unraise your fists (like you are not in fight)
• Press "crouch" button. The character will crouch.
• From Crouching position: try to raise your fists. Character will not react.

I tried the problem with machete and hammer.
The situation is uncomfortable, because you are allowed to hold 2-hand melee weapons and raise them to attack from both standing and positions, and even move in the while! So if i want to attack with this items i need to stand up