what exactly do you think is the problem with it, making the 80prs act up? could it possibly be the way you're wiring things? TA does need isolated channels to work with - just making sure you made sure before you spend money sending it out for repair
filters might be different between the amp causing phase issues, check out the manual and see if the filters are different. might be a solution as simple as switching the polarity on the offending speaker
disregard that if you set the amps to "full" and use 0 filters on the amp and theres no internal filters