in GE delete dischargeTrigger, and make new one(cube primitive, scale to 5 5 5 then tranlate to 0 1.153 -6.269(for example) move new trigger to fillunit transform groupe and dont forget make this figure "Rigid Body" and edit properties( u can get this from fillTrigger for example. and of course dont forget use freeze scale), after that, tank work fine for me.
UPD And dont forget to edit XML for right index.