I've noticed this a number of times too, and every time it includes the same items in common:
1. Unstored calculation field
2. Which references a grandchild table
Something about that grandchild table reference kills it. I find the same thing for calcs on the layout when a grandchild is referenced...
Consider how to arrange things to remove the grandchild reference (after confirming that it is, of course)
Thank's for your help!
You are right. The related fields are calculation fields. So I've changed them to text fields and rebuild the database: same wrong result, even if there are no other tables related to the two tables involved.