Channel imbalance question

Hi - Hoping a fellow audiogoner can help. I noticed a slight channel imbalance in my set-up. Azimuth is dialed in with a Fozgometer. While trying to track the issue down I reversed the left and right inputs on my phono stage putting the left channel from the tonearm lead into the right input. The imbalance went away. Any ideas on what would cause this would be appreciated.

Leave the cart leads reversed. Then swap the tonearm cables around. Is it still balanced after that?
You said: "The imbalance went away". Do you mean that the channels were now well balanced, but reversed? And very importantly: what happens when you return the connections to normal (as before)? Does the imbalance return?
Thanks for the responses. I may have solved this. Will post when I know for sure.