“It's a technical problem of the Luna system that it can't be controlled reliably at temperatures below minus 19 degrees [Centigrade, minus two Fahrenheit],” German MP Gernot Erler told public broadcaster Deutsche Rundfunk.
Winter temperatures in the region would often plunge far lower at the drones' operational heights of 3,000 metres and above, Bild reported, citing a military source.
German drones were supposed to join unmanned planes provided by France and Austria in the Organization for Security and Cooperation in Europe (OSCE) mission to keep watch for Russian troops and weapons crossing into eastern Ukraine.
Erler said there were other "major legal and political problems", including that a German armed military team would have to accompany the drone for a mission under OSCE auspices.
"This is difficult because Ukraine and Russia would of course have to agree, both are members of the OSCE," said Erler. "I've got major doubts that this mission will actually take place.”
If the drone offer does flop, it would be the latest embarrassment for Germany, whose pledge to play a greater global role has been hobbled by a string of technical hiccups with defence equipment.
An internal Defence Ministry report published in September showed that much Bundeswehr (German army) equipment is in dire need of upkeep and investment.
Defence Minister Ursula von der Leyen acknowledged that the military could not currently live up to all its NATO commitments because of equipment problems.
Von der Leyen, Foreign Minister Frank-Walter Steinmeier and President Joachim Gauck have this year all called for Germany to take more responsibility in international crises, with arms if necessary.
SEE ALSO: Germany's military feet of clay