Photoshop 19.1.3 opens images unreasonably small on dual monitor Win10 system

If you hide the toolbar and open the image, does it open to the correct size?

I tried opening several images, some from within Photoshop, and some from an external program. With the toolbar hidden the images opened at a reasonable size. With the toolbar visible they all opened in a small size. They open on the monitor with the toolbar, which also has several panels open. The panels didn't affect the opening size. Thanks for taking an interest in the problem.