Invoice Workbench form skipping fields in data entry

I’m having an issue with my field sequence when entering invoices. I am entering non PO expenses. If I know the supplier # and type that in, I don’t have any issue.  But when I have to search (use the LOV) either in the “Trading Partner” or “Supplier Site” field to pull up or verify vendor information, my field sequence is skipping the “Voucher Number” and sometimes the “Invoice Number” fields to go directly to the “Invoice Date” field after selecting from the LOV.  I then have to backtrack with my mouse to fill in the skipped fields.  Other users of this form