Looks like you were set up to fail on that one fender.
I was always under the impression that epoxy primer was non reactive to the primer/paint you put over it, so you had nothing to do with it lifting off the steel.
Each brand of epoxy primer has a specific topcoat window to get the next coat on, or you need to follow a specific TDS process before overcoating. Do you have the TDS (tech data sheet)for the epoxy primer?
Chuck
