This is the issue I'm having too (flashing).
Not yet tested in other browsers, but in Chrome if I have the page with the promo slider on, open in one tab, then go to a new tab for a while... when I return to the promo slider tab, the image will flash X amount of times.
X is defined by how long I've been away.. eg, my slides are set to change every 10 seconds, so if I go away to another tab then return after 60 seconds, I will get 6 flashes.
Hope that makes sense.
As per your possible solution above, I wasn't using the pause on mouse hover feature (unless it's enabled by default, in which case it's not working anyway)... however I tried adding this into my shortcode to see if it'd fix the issue:
...it never seemed to fix the issue.