I am experiencing the same issue (in cubase 9 pro with macbook pro and I use Nektar Panorama as midi controller) as in the topic below. However, I am not able to ’ translate’ the solution as mentioned above to my set up. Hopefully somebody op this forum can help me out.
https://www.steinberg.net/forums/viewtopic.php?f=146&t=50746&p=667339#p667339
Quote from the topic: “I make my tracks by first recording from my MIDI keyboard and then editing and adjusting the midi notes in the piano roll afterwards. When doing so in Cubase, Cubase automatically creates a duplicate of my recorded note. This happens once for every note.”
I addition to this somehow the volume of the ’ new’ midi note significantly decreases and I cannot change it in any way.