Leaking automatic air vent in the central heating installation

A few days ago I noticed that the automatic vents were leaking, so I decided to replace them with new ones. Unfortunately, the problem repeats in cold water, and as if it was not enough, the mini valves at the manifold also leak. After heating the water, the problem disappears. I have a closed system with an expansion vessel on the DHW heater, a blue expansion vessel on. Where to find a solution to the problem ??

Added after 41 [minutes]:

Sorry, this is an open circuit with an expansion vessel.

When heated, the problem evaporates. Literally. The material may also expand under the influence of temperature and seal for a while. Replace the air vents and re-fold or tighten the mini valves.

Today I replaced all the vents with new ones and nothing helped. And when they were completely closed, there was sweating on the mini valves.

Maybe it was better to replace the air vents with manual ones. They are more reliable (tighter).