Hotspots make graphics blurry in HTML5

My graphics looked fine in output before, but after adding rectangle hotspots for interactivity, the output graphics are noticably blurry.

Are there any hidden settings that control this?

The output options have been set to Default Format: (As Is), and JPG Quality 100.

I copied the graphic so I have the same one with and without hotspots, and hotspots are definitely the cause.