Cubase 9.5 Output on Channels Bug

I like to use the Cuesends for reference tracks.

However Cubase intermittently doesn’t let me change an output on a channel to ‘no buss’.

Sometime when I load a saved project, channels that were previously routed to ‘No buss’ are now routed to my stereo out. Often in this case I’m unable to then select ‘no buss’ as an output as it defaults to another output.