Thanks for the feedback.
I contacted "Officine Malpassi" who are located "nearby" and they claim that indeed the gauge was screwed in to deeply.
Since it is a conical fit, the gauge should be (according to them) loctited into place.
I have just asked them again to provide a repair method since I do not fancy throwing this thing away, but it looks like I will have to.
I hope they will not be offended regarding my comment based on working for 20 years in the quality department of 2 Japanese motorcycle constructors, that they should review the design of this filter king.
After all, the customer is king, not the filter. Sorry, couldn't help myself
And yes Hugo, I will install some correct size clamps once I solved this problem, but unfortunately i messed up the ones I had, trying to fix the potential leaking points.
Again, cheers everybody.