Update fails - returns debug null

Update fails - returns debug null

I am working with biological data & found bug when trying to update a record in a view:

1. I created a form called "Antibody Vendors" with a singe text field.
2. I created a form called "Antibodies" which contains a lookup field to the "Antibody Vendors" text field.
3. Both tables are empty.
4. I import csv data into the "Antibodies" table. This populates the "Antibodies" table, AND vendor names automatically get populated into the "Antibody Vendors" table.
5. Go to the "Antibody Vendors" View and try to do an Update - it fails with a red "null" returned to the UI.

I turned on sharing & editing with Zoho support.

Thanks very much for any assistance.