Sorry for the slow response. Thanks, I understand the problem better now. It could be this has to do with how the “Default” theme contains a lot more native widgets than actual themes do.
Given that, it looks like using a theme more like the defaults, but while still being a theme, is probably the best answer. That way your macro never selects the actual default, and this difference is avoided. That should in theory make menu automation more consistent anyway. There may be other issues with using Default for this same reason, if you are ever selecting commands spatially.