It looks like an upgrade issue. That gray bar is the 'highlight'. Sorry, but have no idea what is causing it.
I have seen this skipping issue caused sometimes by removing the Question Title caption or replacing the Question caption that comes when you first insert the quiz slide. These two captions are actually special types of objects that MUST be present on the slide in order for it to function correctly.
So click around on the question slide and select what SHOULD be the Question Title or Question caption and verify in the Properties tab that each quiz slide has one of these.
If they DO, then the issue must be something else and is most likely something that has been caused by the upgrade.