Almost every A53 Mini's pressure gauge will show a very quick vibration of the pump pressure gauge moving between 6 bar and 9 bar. This is because of the vibration pump in the system. The way the vibration pump works is it pushes pressure in the system by quickly pulling back a tight spring, which allows water in, and then using the force of the spring to quickly close, pushing pressure into the system. Because this is the way pressure builds in the system, the A53 Mini pressure gauge shows all of those quick vibrations of pressure building and water moving through the system in the gauge.
Some common questions we get at Clive:
The answer is no, the pump is working exactly as it should. If you were to put a backflush blank in place you would see the gauge no longer vibrating because there is no path of least resistance for the water to move through, thus making the pump reach an exact max pressure. The only time you'd have an issue with the pump pressure is if your machine can't reach a max pressure while backflushing or if the pumps zenith wasn't between 8-9.5 bar while pulling a shot.
The answer to this question is also no, the vibration in the gauge and the vibration in the pump does not cause the machine to extract in a poor way - a lot of our Cliver's actually prefer it! It is more important to focus on shot times and flavors, because the brew pressure will be constant (despite what the gauge says).
There is a video in the attachments showing what is common for the pressure gauge to do on a La Spaziale with a vibratory pump. You can see there is some oscillation on the gauge and at about 25 seconds the oscillation opens up to about a 3 bar swing. This is because the puck has broken down and there is much less resistance at this point, allowing for more water to flow, making the vibratory pump lose more pressure as more water is flowing through the system. On a La Spaziale with a vibratory pump and pre-infusion chamber it is more common to see closer to a 5 bar swing at the group head due to the preinfusion chamber also pushing water and creating an auxiliary outlet for water flow.