Many apologies to find you in this trouble.
However, would you mind sharing your .muse file with us so that we can investigate and try fixing it?
For sharing the file you can follow the steps explained here - https://forums.adobe.com/docs/DOC-8652 and send the link to me in a private message.
Were you able to fix this issue?
If not please try the suggestion of this thread - Help! Opening Error Can't Copy BPANode from itself after 2018. I need to fix this file. and let us know if that helps.