I feel your pain. It is nigh impossible to pin the problem to 1 exact failure point, could it be congestion on 2.4ghz, ie too many devices in the region, is the 2.4ghz transciever faulty, faulty internal code? Honestly I was at my wits end, desperation is the grandmother of invention, why not try 5ghz...to date, nothing has changed, same devices, same router, same ISP, same same, only changed the laptop to 5ghz, as to why this solved the tripping/resetting.. It is being used as much on 5ghz as it was on 2.4ghz, usage patterns have not changed, my only observation, the change to 5ghz donnu took strain off a weaker overcrowded 2.4ghz system...who knows...I would bet a months subs that Afrihost tested all 3 of your routers and found no faults...
Makes me wonder about the testing/certifying of the product..if you live in a busy wifi region, and we all do, with dozens of networks with many on 2.4ghz, etc, was the routers tested under the same? With 12 or more devices attached to a router, using wifi, ethernet etc?? In other words a real life test, and not a sterile wifi free zone in a lab...Curious...