Photoshop undoes anything I do unless I do it quickly (Photoshop 2020)

[SaraRC]

I have only found one thread on the issue I'm experiencing and it was never solved (and also was from over a year ago). Basically, as the title would suggest, photoshop wont let me do anything that takes an amount of time to execute. Creating new layers, choosing a new tool, clicking once with a brush, those all work fine (though very occasionally they don't), but anything else seems to only work if I do it quickly. For example:
Menus (such as creating a new file, opening a file, save as, adjustments to hue/brightness/etc) - If I spend more than about a second in a menu (for example, to type the name to save my file as) it will do nothing as if i'd canceled out of the menu.

Drawing with a brush - a brush stroke starts and then suddenly stops following my cursor after a seemingly unpredictable amount of time. After this point if I let go of the mouse (or pen when using a tablet) the brush stroke disappears.

Pasting from outside sources simply doesn't work, the option to paste is greyed out and ctrl+V does nothing.

Moving a layer or object - Moving an object too much makes it snap back to its original position when I let go. Sometimes it seems as though moving the object too far makes it do this, sometimes it seems as though moving it for too long does this, I can't really tell.

The broadness of these issues has me puzzled, because I cant imagine anything in the preferences could lead to this many problems. I've tried the following to fix the problems with no such luck:

• Restarting the application
• Reinstalling the application, without saving preferences (this seemed to fix things until I opened the application the second time)
• Rebooting my computer
• Using the legacy new document menu did not solve the problems with creating a new document

I'm using Photoshop 2020 with the most recent updates, and running it on Windows 10.

[Test Screen Name]

It seems to me most likely that another app is "waking up" and taking control of the mouse. It's clearly not related to the tablet because it also happens with a mouse. I am sometimes driven mad by menus closing, but for this I tend to blame my mouse/mouse control. 

I  suggest that the failure to paste is not related. What sort of content are you trying to paste, from what app?

[SaraRC]

On the menus thing, I guess I phrased that poorly. The menu doesn't close on its own, but if I finish my work in the menu (such as pressing OK to save my file or create a new one), it doesnt do anything, as if I'd pressed "cancel" instead.

For pasting, the only times I can remember are from pasting an image I copied from a browser window, but I think that pasting from a different program such as MS Paint would do the same. Pasting seems to only work if it's something I copied from photoshop in the first place.