The BV 238 in Air RB is currently pretty much unkillable. That all the bombers got more tanky, is nice. That some strike aircraft got too, is not so nice. That BVs are taking out entire lobbies around BR 3.7 - not so much. This plane should get its invulnerability tuned down somewhat. And/or moved up 5.0 where it can meet the Qing-6 which is about the comparable thing right now. Maybe higher.
The mindless grinding zombies won, just leave them be and return to hangar when only bombers are left, while they get their SL and RP for free.