Slider slow load after upgrading

My sliders are taking longer to load/display after upgrading to WP 4.0 (from 3.9) and Customizr .23 (from .19). This isn’t related to the number of slider images because the slowest of all is a single image slider – see here.

I’m seeing a rotating wheel while the slider loads which I’ve never seen before (maybe it was always there but my sliders loaded so quickly that I didn’t see it).

Also, while the image loads, the overlay containing the spinning wheel sits on top of the slider so that drop-down menus disappear behind it.

Anyone else seen this?