Can't toggle time base on instrument or audio tracks

This is an issue I’ve experienced for some time (currently on Nuendo 10.2.2 on windows 10): I can’t toggle timebase (between musical and linear) on instrument or audio tracks (yes, I can see/click on the icon but nothing happens).
I can toggle timebase on midi tracks.
The only way I’ve been able to get tempo changes to work is to route a midi track to an instrument track.

I really can’t work out what’s going on and am hoping someone out there has some suggestions?

Here are are some screen grabs.
Instrument and Audio tracks have their time base locked to the linear setting (clock icon). Mouse clicking won’t let me toggle.
Midi tracks are fine - can easily toggle between musical and linear

If this is ever helpful to anyone down the track, I’ve solved it.

Turns out the culprit was third party software; Spatial Audio Workstation (an immersive audio add-on that runs via the project menu).
I’ve notified the developers.