
The biggest problem I've come across with these is broken PCB's from people putting the wrong size of batteries in them, the PCB seems to be quite thin and fragile compared to the bigger 29mm ones.
You mentioned about the quartz, I've managed to find a very good repair for this problem simply solder normal copper wire across the contacts and hey presto a solid mounted crystal. The couple of modules I've repaired like this are running well and keeping good time so its a good reliable fix for them...
