Ah, I actually had multiple issues, but it depended on the share:
1) Some shares, I could read dirs/files, but not do anything else
2) Some shares, I could not access at all (same problem as you, I think?)
3) Some shares I could read and add new files, but could not make changes. Since I backup my families machines to the array (and then sync those folders to cloud), that meant that changed files where not being backed up.
I'm baffled on why the above occurred and why it was not consistent when it failed. So far, I've got everything working again with AD. I did see odd error messages in the logs when this happened, but I did not think to save them. Something about the access belonging to multiple ids.