M5Sime if you decide to abandon the Moca, and given your experience to date I can understand why, take a look at the DF64V as a single dosing option. Reasons:
Very good value for money - the espresso will be indistinguishable from a P64.
Like the P64, very easy to swap burrs, which is a fun thing to try.
Buying burrs for a 64mm flat burr grinder is around 1/3rd cheaper than doing the same for an 83mm and burr for burr, the detectable difference in the cup is precisely zero
Smaller footprint than other top SD grinders e.g. Honne and Duo (pic uploaded for comparision of size)
That said, I’ve not had the issues with either of my Moca SDs that you’ve had and it’s a wonderful little grinder so I can’t help but think that if it was shipped back to Olympia to find out what was wrong, it would be fixed or replaced. Pesonally I’d persist because as @dfk41 quite rightly pointed out, you’re dealing with highly reputable brinds in BB and Olympia.
