By what you describe it shoudlnt matter if you run one sub out of phase or not. If it did it woudl blow all the time..not just when youre bumping. Well it work if it is wired to an individual channel so then ther emight be an issue in your amp..call the amp manufacturer to se eif its supose dot happen liek aprotection mode. try borrowing another amp for just tes tpurposes..