No, I saw the Gefen VGA to DVI scaler on eBay and considered it but it has the same layout and buttons as the AV-700CGA I have, so I’m betting it uses the same chips inside.
You might be right about frame-rate being the issue. This is the monitor I’m using, which I think only supports 60Hz. I didn’t know the OSSC doesn’t support frame-rate conversion. I may have to replace my display with something capable of 70Hz.