Holy hell...I was running into a very similar (if not the same) issue. Kept hearing my dry signal while trying to reamp and it was driving me f-ing crazy. Just spent the last hour and a half troubleshooting and finally solved it, so I wanted to share in case it's helpful to anyone else.
In Kemper's OUTPUT section on page 7 of 8 (available when you press the Output button), there are Aux In settings. The manual says they can be used to feed another audio source (like "an .mp3 player") into the Kemper to play along with.
I have never wanted or needed to take advantage of that feature, yet I found that two of the three volumes were turned up in that section! Turning all three to Off fixed the problem.
Essentially, I was using Kemper's Return Input to reamp a dry signal. However, the volume for the Aux In for my Main Output was turned up. Therefore, it was feeding one version of the dry signal into the Kemper's effects chain for reamping AND also feeding some of that dry signal through as if it were coming from an external audio source that I wanted kept dry.
walkerjerry if you are somewhere out there and still need help, I got you! haha