I had a variety of custom image sizes that I defined by using the plugin Simple Image Sizes (which, by the way, is really easy to use and a time-saver if you don’t want to muck with code). When I used Beaver Builder to rebuild the site I’m currently working on, I found that I could no longer select from those custom sizes when using the Media tool. I deactivated that plugin and just did it in code by adding this to functions.php:
Not to say that the problem is with Beaver Builder; it could just as easily be a problem with Simple Image Sizes. Since that plugin is pretty popular and I probably won’t be the one to have this problem, I thought I’d share the solution.