Hello, there,
Thank you for reaching out to us!
There are many reasons this might happen. Some of them might concern your host and their setup and others might even be a bug. Also sometimes it is a matter of correct configuration. Good thing is that the Adaptive Images plugin does not touch your original images, so they remain safe in their place after you disable it.
Now as a first thing, I would like to ask of you to momentarily enable the plugin and send me the result of the Print debug and Print diagnostics buttons in the plugin settings page, if it is possible. From that I will be able to draw some first conclusions.
Cheers,
Takis
