I've used the feature a lot on the pictures I take with my phone and pictures from the web. From one to a whole folder of images.
I'm just resizing some pictures right now, JPG's and not doing anything else. If I select one picture it works fine, two or more and Directory Opus stops responding.
I've tried a different drive with different pictures and same problem.
I'm resizing, custom with a width of 600, height is left blank. I have the preserve aspect ratio selected and add file name suffix. I did have the use Rotate using Exif information on, I tried with it off and same problem.