Hi all, I realise this topic is a bit old now but I have just had this issue with a 2nd hand sonic port vx that I bought - it worked fine to begin with but then I had the input compression issue you’ve described. I managed to get mine working again by plugging the lead guitar in through the aux in with a stereo 3.5mm to 2 x mono 1/4 inch jack Y lead with the plan being to use this input instead of the guitar input if it solved the issue. After plugging it in this way the guitar input started functioning as normal again. Unfortunately I can’t replicate the issue now to see if the fix works a second time but hopefully it may help someone else (if you haven’t all already binned your expensive paper weights!)
