You can use the "All-in-one admin tool for HCL Notes Mail and Applications troubleshooting," tool which has rebuilding the Inbox of the user. You can have this tool handy on the server so that any future report can be used to fix.
https://support.hcl-software.com/csm?id=kb_article&sysparm_article=KB0032494
Thank you
Regards
Shrikant J