Key editor problem

I have have a project with two VST instrument tracks - a piano and a bass. When I open the key editor of the piano track, with solo enabled, what I see is correct but what I hear is the piano track plus the bass track data, both played through the piano instrument.
Any ideas how this happens?

This happens in other projects also. In this case the piano is HALion Sonic SE and the bass is ABPL2, though this happens with all VST instruments that I have used.

Cubase LE AI Elemenets, up to date
Steinberg UR242
Windows 10 Home 64bit

Edit: I’ve found that restarting Cubase fixes this temporarily. After a while of editing, the problem returns.


Where do you enable the Solo? Open the Track list (Project window), in the MixConsole? Or do you mean the Solo Editor?

Do you use two independent Instrument tracks? Or an Instrument track + MIDI track? Or an Instrument Rack + two MIDI Tracks?

In the key editor, I click on the “S” to make it solo.

Two separate instrument tracks.