Fires, Loads, Does Not Cock
 

At the range today, my 1939 Luger chambers the round, fires, ejects, but does not recock the firing pin. You have to manually recock it. Everything looks normal. What could be the problem? Advice solicited.

Sounds to me like a worn sear / Firing pin engagement.
Check to see if it is Polished and Slightly rounded at the point of engagement.
If ANY ROUNDING is visible under high magnification, Cease use immediately and have this looked into by an expert LUGER REPAIRMAN Several available here on the forum.
Weak sear spring another possibility.
Either can allow the breech to close with the firing pin extended into firing position and could cause erratic full auto firing.
DO NOT FIRE UNTIL CORRECTED!!!!!!!!!
I recommend "Hugh, Thor, Tom H.
ViggoG

Hairy, MOst likely your trigger lever in the side plate, is not allowing the disconnector under it for the next shot. Tom H.