For information, the problem disappeared after the user has done some cleanup in tables of this databases that had invalid fields.
Fields where identified with a warning symbol (red triangle) in the column header. I did not obtain detailed information from the user on the list of changes done and as I was not able to backup the “corrupted” database, I can’t compare tables definition.
Before the user did the cleanup, I tried to export each of the 16 tables, trying to locate the problematic table, but it was possible to export all of them despite the backup was still impossible.
By the way, that means that it is possible to create incorrect data definition in tables (like referencing foreign tables/fields that no longer exist) and this situation is allowed by baserow but do no longer allow backup.
It may be a good practice to not allow invalid fields in tables when they are used for links. Cascading a deletion when a field used as a link is destroyed should be considered…
Thanks for your work