Further thoughts on this, a key feature of composites is the different properties on different axes and this would have been modified in one area only by the repair. Add in the wake turbulence ie varying aerodynamic stress from odd angles and we have a possibility (I'm no expert on aeroelasticity) of a flutter mode unique to THAT a/c subjected to THAT combination of airflow on different parts of the fin.
The problem with this senario is that it is unlikely to be possible to reproduce/model it and hence to definitely include/exclude it.
On a related topic while I believe composites to be the way to the future the current state of the art appears to be just that, an art. Design in metals appears fairly straightforward (I have a degree in Metallurgy. Reading various conference reports on composites I come away with the suspicion that it is still basically cut and try with QC a real problem.