Variable unresponsive when building for android

I use a straightforward system to mute audio in my game which works flawlessly in the editor:


(Elsewhere I have a simple button setting AudioMuted to True or False when clicking it)

The only problem is that it doesn’t work when I build for Android.
I’ve tried making the On Update a coroutine and using On Late Update instead. When doing so everything still works fine in the editor, but not when I build for Android.

I also tried building using IL2CPP instead of Mono, which doesn’t make any difference.

Please help - Am I missing something obvious or have I encountered a nasty bug?

Thanks!

I’m not sure if it makes any difference, but I might add that the visual script pictured above is attached to a persistent game object which is loaded in a bootstrap scene before loading the first game scene…