That's a good question. This sounds potentially very complicated, so a quick fix seems unlikely.So the issue is with the old save... now what can be done?![]()
And at the moment we don't really have anyone active who could give it the attention it probably deserves.
In other words: We could be stuck between a rock and a hard place here.

@Grey Roger: If you use the savegame from post #5 above, are you able to replicate this error?