Unable to Transfer Site Posts from WPMU to WPMU

I am managing my own cloud server but have hit a bump in the road. I recently installed WHMCS MU Provisioning although i doubt that's the problem.

I have 2 Multisite installations, I want to migrate one of the sites from the first Multisite to the new multisite which is on the same server but setup on a different domain name.

For whatever reason, I am able to export/import pages but I cannot export/import posts without getting an internal server error.

The XML file is only 750 KB so I doubt it's a memory limit issue either. There is something about the syntax in the XML export from the original multisite but I can't quite put my thumb on it.

I noticed the permalinks differed from post to post as it is a very old blog that has changed names (same content on a new domain repeatedly).

Please advise,