Affordable letdown, or coincidence?

I have the following problem with this cartridge:
when I insert the cartridge in the faucet while the fixing nut put on such an extent that the
Actuating lever still be easily and operate without jerking, the cartridge is leaking up so that from the
Top of the cartridge water leaks.
If I turn the mounting nut carefully determined so far that the cartridge is sealed, the operating lever is very
stiff and slides nichmehr, but he jerks so strong that it virtually only position fully on, or position
fully there.
A demand for professionals showed that this often happens in these lower-priced products
Trying relubricate the cartridge with tap grease, brought no result!

As the old cartridge, in this single-lever mixer of Italian production, made the same problems, I will
probably soon have recourse to a product with a German name.