Brushing into mask causes rendering issues.

Load in Shadow.psd file, select layer mask and a soft brush with black color.  Video file shows what I am seeing.

Photoshop version 25.12

NVIDIA drivers 560.81

NVIDIA Geforce RTX 3060 Laptop GPU

Files are here since I cannot attahed .psd or mp4 files.

https://drive.google.com/file/d/10ejmIn2VJM9Ao0iZNZn8gxKJB1LxudhX/view?usp=drive_link