Der Eisendrache EE

I was tryna do it solo for the first time today haven’t done it before, made it to boss fight, did phase 1 put rags down, shot the keeper then picked up rags shot panzers and zombies after, did another phase of it, put rags down again and shot keeper again. Picked up rags, and here’s where I need help. There was no more max ammo and also I watched video that said there were 3 phases meaning more panzers and zombies, but this time no panzer spawned and even after killing zombies my rags didn’t charge and so I couldn’t place them down and I died to keeper. And it also felt faster than the time between 1 and 2nd phase.

Someone please advise…