Have you contacted Griz? Their support is very good IMO.
I've had zero problems with my G0555 with riser block.

Yep, they mentioned it could be worn out tires. I haven't used the saw that
much, but I upgraded to polyurethane tires anyway. I haven't had a chance
to really work with the saw since then.

They said I could remove the alignment pin from the riser, but I was
concerned it would be difficult to get things aligned and keep it there
without the pin.

Then also said I could shim one side of the riser, but I was concerned that
might tilt the upper half at a weird angle.

I still might give those ideas a try when I get the chance, just to see
what effect it has.

Anthony Watson
www.mountainsoftware.com
www.watsondiy.com