What is a "decent grade"? 10 percent, 7, 5 or? You have "decent" hills in Eastern Canada? :B Come out west thru the Rockies and then down the mountains in the western states and see what decent is, lol...
When was the last time you inspected the TT's brakes and wiring? TT brakes aren't exactly known for their high reliability.
Have you got the WDH tightened up properly to get adequate wt. transferred back onto the steer axle and is the TT sitting fairly level when all loaded up (incl. truck) and WDH hooked up? Are the spring bars properly sized and not under-sized and causing more flex? I *might* be inclined to consider tightening up the spring bars a bit more or getting a heavier set of bars (depending on your weights & ratings) just for this trip to reduce vertical motion. Also if you haven't, air the TT tires to sidewall max. and truck tires to or near max. sidewall (hopefully LRE & not P type)