Here is a issue where I right click on mouse to ADS the gun in hands.
It starts to ADS and then it cancels, during your in that bug others will see you in ads mode and you can even shoot.
When you shoot you will not hear anything but everybody else can and also the AI's.
You can just click on right mouse to get back out of it and then you work normal again.
This happens randomly so I have not really figured out what is specifically causing this.