Fassie will have negative damage and fire rate after using his "Shot" ability. When this happens, he is unable to shoot more than once. Switching weapons does not fix this, and you simply have to wait for the effect to wear off. I not sure, but I think this is related to the upgrade that boosts the effectiveness when used on himself (which also does not seem to work?)
Step by step of the bug
Step 1
(Maybe) Get upgrade which increases effectiveness of "Shot" ability on self
Step 2
Use "Shot" ability
Step 3
Occasionally, this will cause damage and fire rate to become negative
Fassie will have negative damage and fire rate after using his "Shot" ability. When this happens, he is unable to shoot more than once. Switching weapons does not fix this, and you simply have to wait for the effect to wear off. I not sure, but I think this is related to the upgrade that boosts the effectiveness when used on himself (which also does not seem to work?)