Are you making sure your images are the correct size (in inches) for the buttons you're making?
300 DPI is great (you don't need more than that for color, from my understanding) but if the file just isn't the right dimensions, that can cause issues. Make sure you draw on a canvas that's the size of the button!
For example, a 1.5 inch button would be drawn on a 1.75 inch button template, etc etc. (I have a template for a 1.5 inch button if you want it btw, just DM me. I've been making buttons from home for 5+ years!)
Using a 2000 pixel by 2000 pixel canvas basically means nothing, and could be causing your issue. You wanna go by inches or cm, with the correct DPI, and ignore the pixel sizes.
You could also try not printing outside of the program? Aka, don't export and then print. Try to print from within Clip or Photoshop. (Also, are you printing from a laptop or desktop? I think tablets and other stuff can compress your images and mess with your DPI when you export them, so try not to print from a tablet or phone.) Just a troubleshooting idea.
Make sure you also check your printer settings too so the printer knows the size of the paper and all that.