Photoshop 21.1.2: Tools and features are not working properly

Photoshop is installed on two separate computers, which are both windows. The pointing devices I use are XP-Pen and a Huion. I've made sure the XP-Pen driver is up to date, I haven't checked for the Huion yet. (To clarify, these issues are present on both computers)

The only tasks I do with Photoshop before it goes Wonky is paint/draw. I have Firefox open and there are apps that run in the background though it hadn't been an issue before.

I haven't tried with GPU off, but I'll give that one a try.

After deselecting the GPU, the problems kept persisting.

Firefox has been the target of some pretty sophisticated hacker malware for a couple of years now. So, have you ruled out malware? If you are relying just on Windows Defender and or one of the freebie AV programs, you are essentially unprotected. Malwarebytes is very good and you could download a free trial of their Premium version, scan, and you will be surprised at what will show up. I have seen behavior such as you describe on computers that turned out to be caused by malware ...

Hey Lynne,
Have you tried without these specific pointing devices?  I ask because this seems pretty unusual -- I use the product myself nearly every day in similar ways to what you describe, but I don't have such problems.  But I also just use a mouse.  I know some tablets are particularly problematic.
Now, all that said, this could be some bug which I'm not familiar with.  The zig-zaggy nature you describe sounds like a bug that I thought was fixed, however.  Could you try with a regular mouse and if the problem persists, I'll be happy to help work to get to the bottom of this.
Thanks,David