Guns switching from full auto to single fire unexpectedly

I also have faced the same problem many times, basically all maps, all the time when firing with full automatic guns that has semi-auto mode avaiable.
Other ostensive bug is to change from main gun to hammer or secondary gun when firing an enemy on short distance. It never occurs when the enemy is at mid or long distance.

Very frustrating bug, I've collect a lot of deaths due them.