I have a similar issue with a desktop flow after run in edit mode.
example: Move mouse is preset as shown. I run the flow and realize I need to offset the mouse. I either stop the flow or already have a stop in the flow.

I will move the mouse inside the trailing % to enter an offset, but as soon as I touch the keyboard, my variable is replaced with a fixed current mouse position.

This is acting like a CTRL+Shift is being held down. I thought my keyboard had sticky keys but I'm having the same issue with a new keyboard. This also happens when I'm at my office or remotely connected to my office, so this makes me think it's something in the flow. I have done some diagnostics: clicking cancel to exit the move mouse window, then pressing any/all ctrl and shift keys does not resolve the issue. However, with the window still open, if I press any ctrl or shift key, then exit and re-enter, I do not have this problem.
Any suggestions on how to prevent this issue? I'm ok with tapping a key, now that I know how to get around it, but it is a little annoying.
Regards, Bill.