I've had that happen in B-17s and B-26s also. Once, in 26s, I had the main plane with an engine oil leak on the port engine while my left-side drone had an oil leak in the starboard engine. When both planes finally went down to single engine, BOTH props on the drone stopped completely yet it maintained 250 kts for a couple sectors.
So they actually flew correctly, but the visible prop motion was jacked up.
That second or two waiting for engines on when forced moved to a drone can be a killer if you're under attack at the moment.
