Voltage imbalance at the end of a sixty foot run
It's an open neutral

This sort of voltage imbalance is symptomatic of one thing and one thing only -- an open neutral somewhere.  Fix the neutral issue, likely at a termination although it could be a damaged neutral on a direct bury cable or the likes, and the problem will go away.  Keep the shed turned off at the feeder breaker until then though, as open neutrals tend to be rather...incendiary to electrical equipment.