P: Intermittent brush + mask problems

Attempts to paint with paintbrush in to a mask results in my effect being applied to large, uncontrollable square area of the canvas, disregarding the brush size and features. Large chunks of image are edited, ignoring the brush settings. Toggling layers on off, moving layers around, using history panel, sometimes corrects this. Sometimes must quit and relaunch photoshop. Occurs often and randomly, making work difficult. The latest in a series of cc 2019 photoshop bugs.