On very few occasions (very few) I notice that if I switch from say Pry Bar to EG in the middle of battle, sometimes I will whack the enemy with the EG. Is this what is happening? Are you in the middle of switching?
No, that’s not what’s happening. You could test if the same thing happens for you as happens for me:
Equip pistol and shield in the weapon slots.
Pick Flamethrower as one of your utility skills, on the toolbar.
Now click on the flamethrower or press the key that’s bound to that utility skill slot, so the flamethrower gets equipped and your weapon toolbar (skills 1-5) change into the flamethrower skills.
When this is set, just walk towards a hostile mob until it attacks you. Don’t touch your keyboard here to make sure you don’t accidentally switch back to the pistol and shield skills. Just aggro the mob and see what happens.
What happens here is: the mob walks to me, starts hitting me and at the first or second hit, the kit gets un-equipped and my normal weapon toolbar (pistol and shield) appears. Same happens with the grenade kit. As long as I don’t get hit, the kit stays equipped.
