This is definitely an open neutral problem. The normally-zero-volts-to-ground on the neutral is being forced away from zero due to normal neutral current.
It can be a hazard because what should be grounded surfaces are instead being fed by the 25-or-so volts, and must be repaired ASAP.
Troubleshooting this would start with isolating the section with the broken line by finding the last point where the problem doesn't exist and the first point where it does.
Then start digging.
