it's a weapon of LaGG-3 - type 8 - VYa. as well as 12.7 mm UB Sync. (it looks like u've been killed by this plane, not by B25 ottos).
That's another feature of the DM. Maybe one day, someone will get to rewrite the DM into something that makes more sense.
The problem isn't in Tempest FM, but in FM all other planes. In FHL1.68 we have new strange FM with greatly increased propeller reactive moment.