Subtracting from a mask causes the background to be revealed - Photoshop

[CoolAF]

Is anyone else having an issue with masking in Photoshop? My issue is this: I am masking a subject, and placing a new background behind that subject. After, if I feel like the edges of my subject need some cleaning, I go in with the brush and subtract from the mask around the edges. Lately however, I am having an issue with the original background being slightly revealed in the areas where I am making those adjustments. I will attach an image of what I mean. The only thing that has been working is actually deleting the background behind the subject. Anyone know what might be going on? Is it just a bug that I need to wait for Adobe to fix? Or am I doing something to cause this?

[kglad]

in the future, to find the best place to post your message, use the list here, https://community.adobe.com/

p.s. i don't think the adobe website, and forums in particular, are easy to navigate, so don't spend a lot of time searching that forum list. do your best and we'll move the post (like this one has already been moved) if it helps you get responses.

<"moved from using the community">

[CoolAF]

Much appreciated, kglad!

[kglad]

(you're welcome!)