CR 2020 tape 1 input cutting out

When moving my DAC, placed above the receiver on a shelf, the left channel would cut out. When I moved the DAC to the original position (a few inches forward) the speaker came back on. Back and forth, when I moved it backwards the left speaker cut out, when I moved it forward it came back.
After investigating, a slight movement at the rca connectors on that input (tape 1) causes the speaker to cut out. Sometimes when I move it nothing happens, at other times, with minimal movement at the connectors of tape 1, the left speaker cuts out. No static, just off and on.
Any ideas?

Bad contact somewhere, clean the ground of the rca, pull the unit and inspect the back end of the rca jack for contact issue, may require some slight bending to make better contact. You'll see once it's out of the case.

Thanks for the reply.
The input on the receiver itself seems to have a little more "give" than the ones around it. The plastic of the inputs that extend from the metal casing, surrounding the actual RCA female connectors, seem to move more freely than the others. I'll open it up to see if there are any broken solder joints or something visibly amiss. The contacts of the RCA's all seem to be fine, but I'll put some DeOxit on them and give them a workout while I have it out.