I recently purchased a big box Qtron plus and am having similar issues. Had no problems initially, but after running a stompbox in the FX loop I experienced a tremendous signal drop. Now I have to jump out the FX loop in order to maintain working signal levels. I checked the quarter inch jacks, soldering, etc and did not see an issue. Its not a huge issue to run a jumper cable in the FX loop, just annoying because it originally didnt need this to function properly. Would love some suggestions on how to correct problem.