OS Property will use the Width size of thumbnail picture configure option and calculate the Height size based on width and height size of original picture.
From those coordinates, OS Property will create the thumbnail pictures for agents.
It's your localhost, we need to check it on live server. In additional, please do not provide your site credentials in public forum, please click on menu: Support Tickets at the top to create new ticket on category: OS Property.
The important thing is you should upload your site into live server, so we can check the issue together