Opening Form Deletes Field Value

I’ve stripped my code down to this:
field «RCODE»
select «RCODE»=lvRcode
openform "Payroll Entry"

When the form opens, the value in the first field of the record PanX is on gets deleted.
It will also do this when I toggle from Graphics Mode to Data Mode in the form.
This is a form I ported over from Pan6 (and have been using for probably 20 years).
I haven’t discovered this behavior in any other form.
Is this the sign of a corrupt form, or could I have slipped some code into the form I don’t know about? (there’s very little code attached to the form currently)

Found the problem. A TextList Display object shrunk down and hidden on the very edge of the page obscured by a text display object. The Text List was set to the field that was being deleted, so must have been triggered by moving back and forth between Data and Graphics mode.