I have the same issue with Expression Pedal2. This bug apeared in 2.8 and after the upgrade to 2.81 my Heix LT has the same issue: Just after the Helix LT boots - my preset has problem to work correctly with Volume/Pan block. Like you wrote - Exp2 pedal has 100% Volume in the middle position(half way) and works like yours. I think it doesn't calibrate correctly. When I switch Helix to another preset and then go back to previous one - everything works fine with Exp 2 and volume/pan block.