I was editing functions.php in this article.

The display became decent and I started writing an article, but when I tried to select an eye-catching image at the end, the image file could be loaded, but the preview was not displayed on the edit screen and I could not edit the image size, etc.

After investigating the cause, I changed the theme to the parent theme and was able to edit it.I traced it back from there and found that there was a blank line at the end of functions.php.

We’ve had similar things happen in the past.

Edit functions.php, be careful enough.