Well, I guess you're gonna do it now. lol ..or send the valve back to Germany for warranty.
I had a plunger rod sticking a few yrs back, simply unscrewed the grub screw at the bottom, the spring pops out too, push the plunger out. Check the o rings carefully for a nick or slice... if that doesn't appear to be the problem, then maybe the tolerances are off - need a new valve.
Consult with your german dealer 1st as to how to proceed so you don't void any warranty.
