I am using IMAP on iPhone Apple mail.  I have one day where messages were deleted on iPhone but they keep coming back.  I confirm that they are deleted on server and one Zoho Mail app.

It is only one day from earlier this month.  It has happened before.  I had to delete the mail account on iPhone then re-add to fix it.  An acceptable one time solution but not practical if it happens frequently.  Also annoying to get app specific password.