Dave,

I think that the spring force against the screw and the friction of the O-ring seal should be more than sufficient to keep the screw from moving positions. The lube should be there to keep the O-ring from being damaged during insertion and when adjusting the screw. Possibly, also to resist corrosion. I wiped the thick grease off the threads when I installed the new spring, while leaving a film of it there. The screw moved smoothly and even though the new spring had much more compression resistance, the screw moved more easily and the brew force has not changed in over 6 months. If the screw was able to move I would have expected the brew pressure to decrease over time as the screw backed off.... or not.

Sounds good. I have not had any wandering brew pressure issues either but I have not remove the OPV, just adjusted it. I had an Isomac that liked to wander on occasion and the OPV was relatively light to adjust. Just a concern but it sounds unfounded given your experience.

I just rechecked my machine with the blind basket, I am getting around 0.4 bar difference between the blind basket pressure and brew pressure with the onboard gauge. I would have to put the ScaceII on the machine to verify the pressure. The factory gauges on most home espresso machines tend to be of lower quality to keep the cost down and the VBM gauges are no exception. They are one of my few 'nice to improve' items on the Domobar Super. I am assuming that VBM retained the same OPV and gauges, along with most of the internal plumbing between the Domobar Super and the new double boiler. I don't know how the lack of a heat exchanger would affect the pressure settings but I would guess they would be close in offset. So if you are shooting for a 9 bar brew, you may want to set your OPV at 9.4-9.5 bar with a blank basket.