The bad news is that the fixing lugs break off one by one as the thermostats get older.
I suspect that the plastic next to the hot metal valve becomes brittle and less resistant to knocks.
The good news is that they can be repaired quite easily. I have repaired most of my ten radiator thermostats and so far none of them have failed again.
My method uses UK standard 22 mm copper pipe to reinforce the housing and a 22 mm compression end stop fitting as a former to cut and shape the pipe.
The 2 photos should give you the general idea.
And many thanks to Johannes. Without your software I would have given up on these devices many years ago.


Regards
Bob Harris