The cover art types checkboxes can have different positions depending on the image being edited displayed on the side. Due to some types taking the place of others this can clash with muscle memory and decrease editing efficiency due to user having to wait for the image finish loading.

Unfinished loading:

Finished loading:

In above example "medium" is shifted to the right and "liner" takes it place. Depending on the timing a click could either result in nothing being checked, "liner" being checked or "medium".

Not to mention the (slight) visual distraction it causes for the following forms as well.