I find it interesting it's cutting out with bare wires screwed on. That's pretty much as clean a signal as you can get. That binding post might be shot. Have you tried the second pair (system 2) speaker posts?
Marantz receiver questions
I have a Marantz PM7001 that I'm perfectly happy with, but the speaker wire connections have gotten so sensitive that the speakers often cut out and I have to tinker with the wires to get the sound back. I tried cleaning--nothing doing. Worth taking into the shop or time for a new receiver?
I am playing classical and jazz on cds--Marantz CD6006, Paradigm phantoms. Will I, a non-audiophile, notice sound difference between the PM6007 and the PM8006--worth the nearly 1K Canadian difference?