I'm sure you've already checked it but in case you haven't you might throw a dial indicator on the wheel rims. check it in both planes, axial and radial, I don't know if RE lists a runout spec in the manual, but I'd guess that anything more than 3 mm (1/8 of an inch) could create the issue you describe. And especially so if the run out is vertical.
I *personally* haven't put the dial indicator on the rims, but I am pretty sure my tire installer did when he mounted the tires. And then re-mounted / rebalanced the front, TWICE.
The rims are as true as cheap rims can be, I think. That's not saying much, but there we are.
Thanks for the tip, though. I've often thought that if I had the cash, buying an entire front/rear wheel set and swapping out would give me a chance to eliminate that particular variable.