I'm seeing an odd behavior and I don't know if I've set up something wrong or there is corruption in my FMP database.
Let's use an example with three tables: Project, Contacts and Tasks. On a Projects layout I'll have a portal of related Contacts. The portal is designed to show the name of the contact (the Contacts table has a special calculated field that concatenates the first and last names). It has reliably shown the full name in the portal until today, when I see a list of related Contact names, but the first record in the portal displays the Contact's record ID number rather than the name. I can't figure out how that could happen.
Similarly, for a little while now I've seen the same behavior on another layout. All Tasks are related to a Project. On the Task record layout there is a field (not a portal) with the name of the related Project. Sometimes the related Project field shows the record ID number rather than the Project name.
This behavior is sporadic and I cannot replicate it. Sometimes it happens once in a day, sometimes not for a week.