"Item deleted…" showing when viewing gallery

I like the plugin very much and it works well. Just when I installed it on a different server than my own, I get the message “Item deleted from media gallery”. It differs which images show this whenever I refresh. The images show up fine after I’ve just uploaded them. Also, the WP media manager and the actual website show the images just fine.
It seems to be a problem with the server, but I cannot figure out what. Some parameters I thought might be useful: mysql.connect_timeout = 60; max_execution_time = 30; memory_limit = 64M.
Any clue as to what I should be looking for?

https://www.ads-software.com/plugins/hero-themes-gallery-manager/