Dear Lutenist: I have a little different experiences with Van denHul cartridges. These kind of inconsistencies talk very bad of this cartridge manufacturer.
I ownowned: a Grasshopper III, BB, Frog and Colibri, I have to say that I don't have any trouble with any one of these cartridges and IMHO the Colibri ( low output version: 0.25mv. ) is the best quality performer.
Van denHul has different versions in the same model due to differnt output level, coil build materials, body build material, etc, etc and the different cartridges in the same model catalog performs a little different too.
My experiences with the Van den Hu cartridges and especially with the Colibri tell me that has long breaking time ( over 100 hours. ) and a little " hard " to set-up: tiny changes make a difference on uts quality performance. Normally the Colibri after 300 hours you can send to Van den Hul to a " last " fine tunning with out charge and I can say that when the cartridge return is a winner at the top cartridge level.
Regards and enjoy the music,
Raul.