New posts get 404 with mapped domains

Hey guys,
Looking for some help here.
Domain mapping had been working fine until today. All of a sudden mapped domains are getting 404 errors when trying to view new posts.
As far as I can tell, nothing has changed in the last day or two that would do this. I am currently testing every plugin and every theme to see where a possible conflict might be but not finding anything.
Tried resaving permalink structure as well.

Here is an example:
The mapped domain is
Subdomain is:

As you can see other posts worked and still work fine.
I tested this on another blog with mapped domain. As soon as I deactivated the mapped domain, the post showed under the subdomain url. But it showed as a 404 with the mapped domain in place.

Ever seen this before?
Any help is appreciated. If I find anything that fixes it, I will post it here.