Tow haul mode

I have the truck listed above 1500 extended cab. For the past year or so it randomly slips into tow haul mode. This started happening after I hauled a fairly heavy (at least/200+ pound) piece of furniture across town. I am thinking the load was too much for my truck and burnt up the transmission fluid. The tow haul mode automatically engaging itself was the trucks way of protecting its transmission from blowing/overheating? And has just never been quite the same. When it does this I can not disengage it using the tow haul button on end of shifter. It happens randomly while I am driving down the road. When it happens it seems to downshift considerably depending on the speed I am traveling. When its engaged in tow haul mode it seems to be stuck in second or third gear. I have read that sometimes the tow haul wire in shifter is broken due to placement in steering column and wont work. My problem is the opposite. The only way I can get it to snap out of it is either driving it like a manual or pulling over and turning off the truck completely letting it sit for a min then restarting it or parking it and letting it rest for a good twenty minutes. I have noticed that when my transmission fluid is burnt up and needs to be changed out or is too low or too high that it seems to correlate with the tow haul mode and improve after tending to transmission fluid but sometimes there seems to be no rhyme or reason. Not only is it annoying and frustrating if I am in a spot where I need to go higher than third gear but it cannot possibly be good for my transmission. I unfortunately have never had my transmission serviced and it is at 172,000 miles. I have been advised by several transmission techs to just leave it be as it will cause more problems by trying to service it now. So I just make due by switching out the fluid myself when it starts acting up or I can tell the fluid is burnt up and or needs a refresher. Is this a common problem with Silverados and is it a mechanical problem in transmission or sensors or is it more of an electrical problem as I know their electrical can be fairly iffy to begin with.