[WP Smush Pro] Smush Pro interfering with Revolution Slider?

Hi
When I activate Smush Pro, the site can no longer serve the images in the sliders. Other images are unaffected.
I have Smush Pro operating with other sites without problems. Not sure what is going on but it is quite reproducible. Slider images are shown until I activate Smush Pro, then no images. As soon as I deactivate Smush Pro, the images return. Have tried clearing cache, etc. I have not unstalled /reinstalled Smush Pro. I have deactivated all plugins EXCEPT the WPMU plugins and Revolution Slider and WordFence - and had the same problem
Revolution Slider was upgraded to 5.0x (the same problem was present at 4.6x). Smush Pro is current as of today's update but this problem is unchanged for several days (so unrelated to that update).
Many thanks in advance for any help.
Cheers,
Scott