6 mils over a 9cm radius translates to nigh on 0.3mm of packing at the column base, it's around 0.1 degrees out. I could see it was a bit bent when facing with larger endmills but didn't think it was that far out.
Seems a long way out even for a Chinese tool. Have you checked the column and base for paint or rust intrusion? Is it bolted down onto something level and flat?