Hi Mike, here's hoping things are well with you and your family
Two things needed before I look into this properly (though there's a good chance initial reaction will be to create issue on git to ensure it's fixed before Leia branch is finalised):-
(1) Your log shows that you may not have made the necessary Leia-era script changes (for example, moving your overrides.xml to its new location) - please have a read of the
readme.md and make sure all changes are made as there are breaking changes, then provide an updated log if you have to make any changes - particularly important to confirm whether the necessary changes have been made, as the log looks suspiciously like it's trying to load the overrides.xml from the wrong location for both cases...
(2) Please give steps to reproduce - in this case, what particular changes have you made that aren't being saved? (It looks like an attempt to change widget) Is this the only situation you're getting the error with?
Cheers