On my M-Audio 88, the sustain pedal also increased the volume when used.
In another thread, somone mentioned a potential explanation of the control (the sustain pedal) firing events, trigering different controls.
Now, the M-Audio is setup as instructed by Reason. This was done, when it was discovered by Reason, it prompted an instruction, for the user to load nr. 10 on the M-Audio device. And after that, the volume incerease have been anoying me ever since.
I found the solution to recall the 10 preset program again, and that seamed to be the solution. Maybe it is doing a device reset??
Hope this helps