Whenever I do a mixdown (midi) of midi-instruments in Cubasis, on reloading (in Cubasis) the drumkit is replaced by the Studiokit?? I’ve seen other instruments (bass) change as well… Is this caused by General Midi matching?

Yes, the GM standard instruments are more basic than the instrument library Cubasis provides (e.g. GM only has 1 drum kit).
So, for instance, you export a file containing an Electro Kit track → turns into the GM Standard kit → reimport → Cubasis’ Studio kit is the closest match to the GM Standard kit.

On a related note, when exporting to MIDI, the maximum pitch bend range is reduced to 2 semitones.

Thanks again, Uphys!