It might be worth going back to basics to efficiently trouble shoot …
Record one keyboard out via MIDI to Cubase MIDI track in to Keyboard in to Keyboard out via Audio to Cubase Audio track in. New project, no plug-ins, etc, especially on the master channel.
Do you hear “clipping”?
If so use your meter “input” and “post pan/post fader” output views on all audio channels (two of them in this case) … make sure there’s nothing close to 0 dBFS.
If you still hear clipping it might be speakers, or interface audio out issues. Or something else, but at least you’ll have eliminated gain staging issues as a potential cause.
PS - could not open your link …