I was on freq and it puzzled me I admit.
7700 was at the request of French ATC and he requested fuel dumping for which three minutes would be needed and this was granted upon descending to 30,000ft. Upon enquiry from French ATC as to the nature of the problem the repeated reply was "a mechanical problem".
After a few minutes French ATC said that Heathrow ATC wanted to know the exact nature of the problem. With what seemed like some hesitation the UPS replied with something like "we have been told by Company that we have a mechanical problem but we do not know what it is".
Cue puzzled expressions across the sector.
Shortly after we left the frequency and spent the next hour speculating and theorising. Never did come up with a theory.
I'm sure it was all perfectly reasonable but it did sound curious.