WB627
Having worked with F700's a lot there are several things here.
1. The F700 would not list huge amounts of detail on the repair. It would note it had been done - that is all. It would have been updated if the whole component had been changed though (so a whole wing or whole aileron etc), not a panel repair though. It is perfectly possible to splice a whole section of wing on to a damaged wooden aircraft including the main spar but usually it is a major job and takes a long time to do and you need jigs to do it. I think it is unlikely that this sort of repair wold have been done if the crash was 16th and the previous accident on the 15th - time would not allow.
2. The aircraft would have been repaired to an approved repair scheme (of which there were many) so not just any old fix would be allowed
3. Only minor repairs were done at a unit level - the serious repairs were done by specialist units or often returned to the manufacturer for repair - in this case that did not happen (obviously)
4. All repairs were (are) cross checked by other tradesmen and then supervisors - the likelihood of a poor repair being returned to service are tiny
5. Sadly it is a fact of wartime that many of the aircraft on Training units and OTU's were old and 'war weary' and often combined with inexperienced crews there were many accidents that otherwise might have been avoided. I think almost as many people died training as died on Ops.
If your relative was around today I think people would tell him it was not his fault in any way shape or form, and that sadly these things happen as part of training (as he would be only too well aware). The fact that it was his friend makes it doubly sad, but based on what you have found out there appears to be no real link between the two accidents.
Lets hope that would have set his mind at rest.
Regards
Arc