Product images no updating in Magento, staying as watermark

Having a bit of a weird bug in Magento that I can't quite figure out.

When trying to update product images in admin the images don't update on the frontend, instead the default 'no image' watermark appearing instead still.

What is odd though is that when I select 'Base image', 'Small image' & 'Thumbnail' then save the page refreshes and then only the thumbnail option is selected.

Not really sure what is causing this but to help solve it I have already done the following with no success:

• Changed /media permissions to 777 recursively


• Changed /media permissions to 755 recursively


• Renamed .htaccess in /media

And after each of the above I have cleared all caches and restarted the server (just to be sure).

Also, /media is owned by www-data and PHP memory limit is 512MB (is that good?)

The site is Magento 1.9 CE on AWS ~100k products.

Thanks in advance for any help it's greatly appreciated!