Hi, I'm having literally the exact same problem. I like to edit things quickly and MS Paint is my go-to tool. I just now went to edit an image and print it out, and my page orientation defaulted to landscape in Page Setup. I simply clicked on Portrait to change it and the program crashed my edit and reopened blank. It does this every time I try to switch the orientation to Portrait.
My MS Paint version is 1803 (OS Build 17134.407), and I'm also on Windows 10 like the original poster.
Any help would be appreciated!
I've just installed a new printer so that was my first suspicion (it's an HP ENVY Photo 7155), but I saw this post and thought I'd try my luck here first.