I followed these steps (helfpul, thank you). I was careful to set the grinding ring back to the standard setting as described, however when reassembling, the coffee comes out watery. Sure enough I take out the drip tray and the grounds are very large.

I did notice that the burr and the ring were quite damaged/ rusty.

Would you suggest that the grounds being far too large is more likely to be due to the reassembly being incorrect, or the stones being damaged/ worn?