Step Solo not working regularly

[macs4music]

Hi all,

for some reason the step solo doesn't always work for me. When working, I can use it with the editor / librarian and the step is solo'd in both. However, randomly it stops working; it flashes the step but then moves on through the sequence. Similarly, If I try to right click in the editor on a step it won't let me tick 'solo'. If I reboot, or disconnect from the editor / librarian that can help but
I also have issues when no editor is connected.

Is anyone else having this issue and if so have you resolved it? I'm on the latest OS and tried reinstalling but it didn't make a difference.