This is a regular occurrence for us. Sometimes we have to copy the Activity that is running a hamster wheel sync and save and sync the new campaign. Every time I report to CC, they are like "It appears to be working now"
Not very helpful I know, but that's our current state of this issue.
If you clone it should have all the experience html/css/js. This is a pretty good work around. Just like taking my car to the mechanic as soon as I hit 'send' it started working. I'm glad i'm not alone though. It'd be nice if we could clear the queue and resubmit the change. I'm not sure how much work would go into that on adobe's end, but dreamland is a nice place.