I sometimes see issues when switching between add/subtract when using the brush when selecting the subject. If I subtract from the subject and then I add to it in other places, the part I just subtracted gets added back again. This doesn’t always happen.
Also, I see when I am painting to subtract, the brush adds back near the part I am erasing.
Let’s try updating you to the most recent version release to see if this resolves the issue.
Please make sure you’ve also turned off any firewall, VPN, or proxy that may be on your computer. These are known to block the installation. Also, make sure there are no settings or configurations in your OS system that could interfere.
Try using the appropriate OS system link to update: