Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
Obviously, whatever reaction there is to exactly which button or control you Cancel the record with (- cancel as in cancelling a Selection? or cancelling a record's Playing ? and with what button?...) ...whatever button and whatever reaction, a severe shorting of the electrical works is involved. The question now remains:
Is it a mechanically induced short, from a part being bent?
Or is it a wire that has gotten loose and only that Cancel control or button (whatever it is) moves parts that cause the short against the loose wire?
Or is it a part that 'cancelling' activates, but 'back' and shorting micro switch do not activate?
In order to judge what is wrong, I suggest watching carefully, and comparing, what happens and what moves where within the jukebox, when you press Back as opposed to when you press Cancel (or whatever button it is.) Whatever difference there is, should indicate the problem's location or cause or both hopefully.