Looks like you set an inside bleed value.
Thank you very much Peter! This has been an issue I have been trying to fix for quite some time on this project, finished it early and it's nearly late because of such a silly issue.
It really isn't a problem most of the time. It only shows up when you have content closer to the spine than the bleed allowance, and even then, unless there is creep added during the impositon, or you need the bleed for something like wirebound, it will never make it into an imposed flat.
In a case like this where you have a break at the spine if you actually need inside bleed you need to break the spreads apart and extend the art. See InDesignSecrets » Blog Archive » Breaking Pages Apart to Bleed Off a Spine
The reason I couldn't initially find the issue is as you said, having inside bleed on previous projects didn't encounter this issue.