Let's see...
the engine nacelles with the chin radiator look like Jumo
The chin radiator makes it look a little like a Jumo, but it isn't.
The funny thing about this is that only two planes of this type existed and the other one indeed had Jumo engines
it has flame dampeners so it is a night ops plane
Those are no flame dampeners.
4-blade prop would indicate it is not an early war bird
No that's misleading.
This bird's maiden flight was in 1939.
it seems to have spatted fixed landing gear???
Yes because for development purpose, speed wasn't the main concern and drag didn't play such a big role in the desired flight regime.
High altitude x plane, German. A Henschel?
Absolutely true.
Which one?
Best regards - Mike