I have found something interesting and I was wondering if anyone has run into the same issue. The last two 123's and one Primus 71 I have fettled has had the same issue. All 3 I have totally been broken down and cleaned but when I put them back together they have burned very poorly. As with all these stoves I know it's due to a loss of pressure as it heats. All of them I have used a cap gasket from the Fettlebox which is 10mm x 18mm. When I switch it to a .7 x 3/8 gasket they burn beautiful. I'm at a loss as to why. Not a big deal. I keep both on hand.