PSE2023 cannot drag top of window to resize

I've just purchased and installed the upgrade from PSE2022 to 2023, running on Windows 11 21H2. When I position the mouse on the left, right, or bottom of the PSE window, I get the expected double-headed arrow pointer and can drag that edge of the window to resize it. However, I get no such pointer when positioning on the top of the window, and cannot drag to resize it. I can grab the title bar and drag it, and I can position the mouse mouse on either top corner of the window and get the diagonal arrow to drag both top/side at once, but I can't drag the top of the window only.

If I open PSE2022, which is still installed, I don't have the same problem with it. I get the double-headed arrow on all sides of the PSE window, and can drag each side individually.