Don't specifically know the transistion altitude at the specified location, but if it is rather low, the ground equipment may well be at fault.
Many locations in Europe/UK still insist on using low transistion altitudes, and clearly need to rethink the idea of using a higher one.
Will they?
Not likely any time soon, I'm afraid.
Old habits die hard.
OTOH, the crew might well have climbed higher than cleared, and if the rather low transistion altitude was the cause, the local ATC unit might well ask why.