The problem was not the upgrade of WordPress to 4.0 although I did also upgrade to WordPress 4.0 it was the upgrade of the plugin which was around the same time.
The problem was the plugin upgrade reset the “timeout” settings. I am assuming you are using the JSJ Gallery slideshow.
Go to Settings > JSJ Gallery Slideshow and go to the “Simple” tab and set the timeout to the amount of time you want between each transition (in milisseconds). 3500 sounds like nice number.
