To reproduce:
1. Create a table or collection and put a drop-down field in it
2. Hook up that field to another field in the table or collection (e.g. when you select a name, it populates the second column with the user's title)
3. Add one or more rows or items in the table or collection
4. Delete first row/item (doesn't happen if you remove second row/item or later)
5. The <option> elements in all the dropdown fields in the table/collection will be completely wiped out, along with the user's selections.
This does not happen if there are no lookup rules attached to the table.
Forms 9.2.1.