JahLaza I also observed the vent movement of the lever was very stiff after regreasing with molycote after this procedure last week. I disassembled the release chamber (bottom part?) of the group head to see if anything was sticking or any dirt there but didn’t see anything. Still stiff when I lower the lever at the end of the shot. Just adding this in case it could coincide with the stated problem
The lever movement shouldn’t be stiff, that usually indicates wear, or possibly you made an assembly mistake? However from what you say it started before that. So the stiffness of the lever may not be related at all, just coincidence and wear.
Or if you disassembled for lubrication and cleaning a while ago, perhaps you made an error e.g. got the springs mixed up?
I say all this because the actual Viton seats in the valves are usually good for 7+ years in E61 groups and wear on the cam followers wouldn’t cause the vent to leak, although it would cause stiffness and if really bad, make it difficult to open the vent to depressurise.
It might be that for whatever reason the vent valve/group valves and springs might need replacing to stop this happening.
