Mail Smartmailboxes will not save changes

Hello! Mail recently began not saving and changes to the smart mailboxes. If I reposition a smart mailbox, add criteria or rules to it, they will not be saved if I close the app and reopen. The other regular mailboxes do save changes in position etc. So this seems to be specific to the smart mailboxes.

I've seen a few post from several years ago, but they aren't very clear on how to repair, or they are from older OS's.

I have tried:

• running Disk First Aid to repair permissions etc.
• removing SmartMailboxesLocalProperties.plist (all smart mailboxes disappeared on relaunch, and reappeared when I put it back, so clearly this file holds the mailboxes themselves, just maybe not their positions and rules)

Is there a pref's file that could be damaged? Attached is a view of MailData folder found in ~/Library/Mail/V5/MailData. Which file is it? What should I try to fix the issue?