When users are entering dropship invoices via the AP20.1, it flips to the MA43.1. After inquiring and adding the line needed, it stays on MA43.1 instead of flipping back to the AP20.1 screen.
Has anyone else seen this happen?

Yes, that is usually how it happens for us. I believe the only time it flips back to ap20.1 is when entering a service invoice. All you have to do is click on the invoice button and you can get back there.