Quick Selection tool no longer working

My quick selection tool has suddenly stopped working. It's doing three strange things, the combination of which has made the tool completely unusable. 

1. If I have multiple layers and one layer has people in it, no matter which layer is selected, when I do Select Subject, the tool always selects the people. So if I am isolating something from another image that I want in my final design, I cant get the quick selection too to select it with Select Subject. This has never been a problem before. 
2. When trying to select something manually, the tool always selects the entire image. I can't click anywhere and select one specific thing in the image. 
3. The tool oddly does seem to work with images of people. If I am selecting an item of clothing on those people, I can manually select it. However, it is incredibly slow. Every click the computer stops to think. I get a blue bar showing the progress of the change, and it takes between 5-10 seconds for it to register every click. 

So as you can see, I have no way to select pretty much anything which is making my workflow about as impossible as it can be. This has tripled my production time. 

Any ideas on how to fix this?