It would seem my code can play that test DSF just fine. Well, at the very least I don't have to worry about those SCSP copy/paste bugs smile

As for AEG monitor... I don't think it can be fixed. AO treats AEG like a fancy addition to volume control but it's way more than that.
I do have an idea though: AO only keeps track of the EG volume and uses 10 bits for that, meaning it can go from 0 to 1023 (and back). However the AEG internal state counter range is only 0 to 959. Try either masking, or better yet - rescaling, the value that's being put into the monitoring register. It's a hack but it might just be enough to fool the driver.