Brush switches to eraser automatically

I use a general hard brush to draw and for the eraser I use a general hard brush as well. After some time the brush switches automatically to the eraser tool. I press "b" to switch back to the brush. As soon as my pen touches the Cintiq 22 inch it switches back to the eraser. I switch to another brush and the problem remains. If I save and restart PS the problem is gone. But it eventually comes back ... 

Mac OS 12.6

PS 2023 24.0.0