I sent my GG6 in for warranty repair/replacement on Monday. I think it is the brushes finally wearing out. The rep said most likely they will send me a new polisher in return. Sounded like maybe only power cord replacements is the only repair they did. There would be a $30 upcharge if your polisher was not the latest version.
Never recalled an upcharge if your polisher wasn't the latest-greatest model, but what do I know? Also, was once told by them that no bill of sale was needed to be provided, but now not sure if that policy has changed?
I once shared a story I think, about my little Griots 3" polisher that I bought brand spanking new from a seller for the tidy sum of $63 shipped.
After an hour's use on a couple very small areas, just basically to try out, the machine seemed to had gotten much louder, and rough sounding from when I first started using it.
I decided to operate. On the GG 3", there is no outer access to the brushes, the unit must be opened.
The brushes, with basically zero wear on them from such little use were cracked in half. Good thing I had that spare set of brushes that came with the unit. They were tricky, that once after being installed into their receptacles, they had the propensity of wanting to pop out when re-assembling the two case halves, they wanted to partially pop out, thus not a proper installation initially, I suspect that's what happened when the unit was assembled at the factory.
I rectified this design flaw that by use of some electrical tape to retain the brushes in their receptacles, they then stayed put upon re-assembly as I did double check by assembling, then disassembling again.
Lubricating Grease was also not found where it was needed at the gearhead, tons of it in there, but not doing the gears much good, they were bone dry. Cleaned all factory lubricants out, replaced with a proper amount of full synthetic Super Lube Grease. Much better! I suspect no further trouble from this unit for a long time.
My advice is if you ever feel the need to disassemble one of these units, do the job neatly, professionally, do not cause evidence of the unit being dis-assembled with buggered screws, chewed up cases, etc, from shoddy attempts lest you'll likely void any-all warranties.