How do I turn off additional brushes being created in a mask in Lightroom

[precise_future6C12]

I'm running:

Windows 11
Lightroom Classic 12.5

When I create a mask in Lightroom and then select either Add or Subtract from the created mask and try to edit the mask I now get additional brushes rather than just editing the mask. This is new behaviour in Lightroom that I have not experienced before. Typically I can either select the keyboard shortcuts or menu items. I used Lightroom at the office yesterday to edit about 60 images with the normal expected behaviour, today at home, not so much but it did work correctly the other day when I was editing earlier on in the week.

I've reset the preferences and checked them, again, and can't see where the changes are that are exhibiting this behaviour.

[GoldingD]

Looks/sounds like normal.

'You click on Add, you have to select what to Add, some brush. You select Subtract, same. I note that one brush indicates a subtract. If you select one of those brushes in your mask, your built up mask, it may do as you desire, if instead you click on Add again, yet another brush will occur.