I haven't experienced this yet - but some aircraft are designed to reflect engine failures. I've had it happen to me a couple of times with German two-seaters. things were going quite well and then suddenly my engine died.
the fact that it's happened to you twice makes me wonder:
did you reduce your fuel mixture as you gained altitude? after your climb over 7,000-10,000 ft of altitude you should lean the fuel mixture to prevent this sort of thing from happening. you're possibly flooding the engine with fuel and killing it. if that happens you can try restarting your engine as you descend and it will usually pick up again.
if you DID reduce your fuel mixture this is probably a simulated engine failure which happens randomly. better to leave your engine off and make the best of it. I've tried restarting it, and sometimes it leads to your aircraft catching on fire. so far all of this sounds.. pretty normal.
might want to wait for somebody who flies the DH2 really often to weigh in on this. but it sounds okay to me.
But the engine doesn’t die, it stays running
The first time it happened I just shoot down an observation balloon, the second time I was hard turning to engage a flight of Eindeckers.