MySQLi Insert Record combined with File Upload - File name not saving to database?

Aaargh. I've tried every option in the "Upload Files" section in the Dynamic Data window:
Server File Name
Server Simple File Name
etc

...none work. The file uploads to the server and on our confirmation page, despite the Save ID to Session not actually appearing in the Bindings panel we CAN call the session ID and have the correct database ID displayed. Checking the database, other form field bindings are being saved, but not the file name. Assume this is some issue with combining File Upload with MySQLi Insert.

I attach the page with "Server File Name" selected as the binding for the image field in our database:
<?php echo $WA_DFP_UploadStatus["WA_UploadResult1"]["serverFileName"]; ?>

Hope you can sort this for us.
Thank you.
NJ