Dear Alex,
one more thing worth checking before I ask for your admin credentials: since you have only “thumbnails” selected for the Recent Posts Slider, please check if the posts in the concerned categories do have featured images (see the Manual page 4 on how to set featured images for posts) – otherwise the slider will return empty images. If this does not help, please provide your admin username and password to support@satoristudio.net – I will take a closer look at the back end and do my best to solve the issue!
Sincerely,
Andrew | Satori Studio