I just stumbled on this bug after completing a trade with someone.
Once I equipped the shield, in this case, a Stop-Gap with Anointed Beastmaster “Grants an extra charge of Rakk Attack!”, the ability displayed 3 charges in Rakk Attack on the HUD when I left the menu. All three Rakks were usable in quick succession, in line with the ability granted through the shield.
However, when I changed maps, the charge amount was reduced to 2. Initially I thought it was a visual bug on the HUD, however I confirmed that I could only launch 2 Rakk in succession, and not 3 Rakk like prior to the map change.
I unequipped, then re-equipped the shield, and the Rakk Attack charge counter increased back up to 3, where I could fire 3 Rakk in succession again.
Please advise of this bug, as having to re-equip a shield for each transition is cumbersome. Thanks!