Details window sometimes doesn't close without multiple clicks

 I"m in the process of setting up this software, and I've noticed an issue. When viewing documents/details, sometimes the details popup window will not close without clicking on the x multiple times. Is this a known issue? If you want to see what I mean, go to this page:  testvvfh.vvfh.org/index.php/books/e-bookstore/free-books and click on details for any of the books. If it closes immediately, try another one.

BTW, I'm on a 2021 Mac Powerbook running Monterey (OS 12.5.1) and using Safari Version 15.6.1 (17613.3.9.1.16). I'm seeing the same issue in Google Chrome Version 104.0.5112.101 (Official Build) (arm64).

I'm loving this software, btw.

   

Update. I've noticed that, if I can see the page behind the popup it closes right away. But, if the background is black (as in the screenshot) it takes multiple clicks to close the window.