> Has anyone ever figured out where the problem actually is? I would suspect
> cracks in the silver ink where the tails flex. This could be repairable by
> painting on some more silver ink with a fine brush. ...

The silver ink ideawill work for some of the boards, but the main
(catastrophic) problem is that the flex becomes so brittle that it will
actually break/crack all the way through. If the cracks are very close to
the end, then those can just be trimmed off - but if they're farther back,
then the repair is much tougher.

In a nutshell, the membranes themselves generally hold out - but the flex
from them fails (there are off course exceptions to that rule...)