Why would a powershift not slip when your holding in brakes. Especially in reverse gears? What are they doing that they are in 3rd and 4th gear reverse with the brakes on? Are they saying it won't reengage after the brake is released?
putting the brakes on simulates a load what is strange and what marks saying is that you don't often pull anything or generally use reverse much so it should never wear out the clutch packs that wear first are generally the working field gears