I just bought a brand new Marshall code 50 amp for my guitar, but when I connect the cable to the input of the amp I have to push it in to work, one end of the cable needs a push so the amp connects to the guitar, but somehow the other end of the cable connects only if I hold it pushed in the amp, if I let go it disconnects. I use a Boston cable and I don't have that problem on my other amp (marshall mg15gfx).  I did the last filmware updates and reset my amp 1 time. Since 1 end of the cable works, is it a big deal or can I just continue to use only the part of the cable that works? What should I do?