I am also encountering the same issue with your theme using version 4.4.2 wordpress and your latest theme. Image thumbnail will not render but the upload does go through and gets all sub sized images created.

We have our site on Godaddy Managed WordPress and have had them up the memory limit and still have the same issue where the image will not get created in the media gallery.

I did find out if i disable your theme and upload through media it works without issues.

Let me know if there is anything else.