Illegal parenthesized reference: COMPACTMAILRULES

One of my users is getting the above error message opening their mail file.

I’m finding a lot about renaming the bookmarks.nsf for other reference issues but was wondering if anyone had come across the COMPACTMAILRULES problem?

Thanks

Subject: Solved

Renaming bookmarks.nsf to bookmarks.nsf.old forced Notes to create a new one and this fixed the problem.