While running this forge today I noticed some of the Harpies in round 2 were dropping 2 to 3 forge batteries instead of the typical 1. It was not consistent, but would typically occur after being struck with continuous/pulsing damage. Sometimes the bonus battery would drop while it was taking damage, other times the bonus battery/batteries would drop after it died. I noticed this while using the breakneck when rampage was active, when using my titans void magnetic grenades after the second blast, using my titans electric pulse grenades during the follow up pulses.