I just purchased a Mini Vivaldi II from Clive Coffee. Ordered with custom walnut side panels; what a difference it makes wrt the looks of this machine. I have a problem though. After pre-infusion (passive) the brew group gauge slowly moves towards 9.0 bar, but then starts oscillating wildly between 7.5 and 10.0 bar. It does not stay at 9.0 bar like I've seem other Mini Vivaldi's on web videos. Then after extraction stops the gauge stays at ~9.0 bar until I run a flush cycle after which the gauge returns to ~0. I visited the CliveCoffee store in Portland OR and showed them a video I took. They agreed it was not supposed to do that. Any ideas what may cause that behavior? I will call the service dpmt on Monday, and hope to get more information them. The attached pic is my best attempt to show the gauge oscillation.

I'm suspecting your grind is not tight enough. How does it behave with a backflush disc in?

Does the pressure stay at 9bar with a blind filter or is it oscillating as well.

Also check if your pump goes quiet with a blind filter.

If it is oscillating there could be a problem with the OPV's spring, in some cases the problem is the gasket that is not sealing.

If it goes quiet you have a bad pump, that needs to be replaced.

But please check that your water tank is entirely in it's place, you might need to push it a bit harder then you might think is necessary.

Thanks for the observation. I actually tried that. Didn't help; the gauge actually oscillate in a wider range with the blind disc on..

The gauge on my Mini Vivaldi has been behaving excactly that way too for the last couple of weeks. The shots are still very nice, so I haven't yet tried to solve the problem. However, I would really like to know what Clive Coffee thinks is the problem.

TM, I was deferred to Chriscoffee service dpmt and will call them tomorrow. Wil let you know what I find out. My shots are ok but not ideal. I'm doing 18 g and getting about 1.5 oz in ~ 28 secs. But the shot is a little on the bitter side. So I thought a possible group pressure issue could be affecting shot quality.