Well as i said i unfortunately i didn't save the replay but i was able to redo it in cheatmode-skirmish after sending 20 stormpios with flames to dead. It seems like in some cases the deathcrit on the flammer just doesn't work properly and the unit can get out but without its flamer. I did save the skirmish tryout tho but i don't know if you could watch it.
First of all i didn't save the replay (forgot about it) - anyway i just had the bug that when the last model of a stormpiosquad "exploded" due to his flamethrow, the last model didn't die. In exchange the squad still showed the "flamethrower" upgrade after retreat but they lost it and it can't get upgraded again.
Plus is the flame hetzer intended to have same pop cap as a panther? The mp drain is pretty high with 16 pop for its performance.