The sub weighs 15 kilos. The tip of each of the four spikes is roughly 1-1.5 square mm. That's roughly the equivalent of 1.5-2.25 metric tonnes per square inch pressing in to the floor per spike.
Yes, the bottom driver is the main driver, so there's some up/down force in reaction to the driver movement. However, I think we can safely presume that REL knows what it's doing when it designs subs. Making a sub that can't keep still under maximum load doesn't seem like the most sensible thing to do, and it would be picked up like a flash as an issue once the product is/was released. T2's have been around for about 7 years, and there's a distinct lack of threads shouting about this as an issue.... so putting all that together I'd still be looking at other causes. It just seems really odd you're having this issue. I wonder if you aren't hearing the driver hitting the end stops?