Arturia Keylab MK2 Custom Midi Remote Script ( MKII )

Ok, uncheck the MIDIIN2 port from the “All MIDI”. You should have it as shown here:

But I don’t see this really connected to the issue you describe. Which port do you have selected in your instrument tracks? All MIDI or maybe a specific one (in particular the MIDIIN2)?

If all the above don’t work, you can try closing Cubase, turning your Keylab off and then on again and restarting Cubase. Note that my script works with the DAW port only and doesn’t conflict in any way with the Port 1 which is used to send notes to the DAW.