I have been able to replicate this issue as well (it wasn't difficult).
There also exists a tracker item for this: https://tracker.moodle.org/browse/MDL-67358
I'll try to post more when I know more, but for the moment, it appears to happen with a variety of plugins and at different levels. For example a block will affect a dashboard page with that block on it more than say a quiz question type. (which is logical).