Leaking Valve on Viessman CWO Expansion Tank: 2-year Install, Water Pressure Jumps 3-6 Bar

Hello,
I have a 2-year CWO installation on Viessman. Water has been leaking from the valve for several days. Not always, but in large quantities (the photo shows the valve in front of the tank with a blue tap).
I also noticed that the blood pressure started to jump strangely. By default, it stays at 3 bar, but sometimes it jumps up to 5-6 bar.
As of today, I only use domestic hot water and it is leaking. I'm afraid to fire up the floor heating.
Can anyone tell me what's going on?
Am I able to deal with it myself?

This silver bubble is a diaphragm vessel (damper). When the shock absorber is empty or damaged, you have symptoms.
How to find the cause:
At the bottom of the silver bubble there will be a cap and a cap under it or valves (like in a car). They press on the center of the valve, water may fly (damper damaged and necessary changes) or air hisses / nothing hisses (damper good but empty).
When the shock absorber is empty:
You turn off the water supply to the house. You turn on the hot water tap, connect the compressor to the shock absorber and pump it until you get about 2.8-3 bar on the pressure gauge of the pump gun. While pumping, tap water will start to flow (air fills the damper). Stop pumping when the pressure of the pumping gun is stabilized.

I checked. Air escapes from the valve when the needle is pressed in. The pressure gauge shows slight pressure jumps from 3 bar to 2.9 bar as I push the valve. No water comes out of the valve.
And what's next.

Magister_123 wrote:

You turn off the water supply to the house. You turn on the hot water tap, connect the compressor to the shock absorber and pump it until you get about 2.8-3 bar on the pressure gauge of the pump gun. While pumping, tap water will start to flow (air fills the damper). Stop pumping when the pressure of the pumping gun is stabilized.

And that was the reason. Thanks

Is it the same when installing on the garbage can and is it just any faucet or some at the stove?

dynekpimp wrote:

Is it the same when installing on the garbage can and is it just any faucet or some at the stove?

If you have the installation done correctly, the procedure is the same.