I am still confused about what I am supposed to do to fix the issue. I read the documentation and tried out different options, but the irregular size of image for product is still shown as before.
You forgot to provide the URL of the website with the login details. Please provide the admin panel login URL of the website to let me assist you further.
I have found that you are using the old version of the theme, please update the theme and plugins to the latest version then check the site and apply the image settings. I am sure your issue will be solved.