This issue has been identified as a product defect with ID 326648, to improve the way Change Auditor enumerate and resolve the network connection between the coordinator in the root domain and the foreign forest servers topology. A fix is expected to be included with the next hotfix of Change Auditor after the 7.2 release.
WORKAROUND:
Option 1:
Fix the broken foreign forest sites by either adding the missing servers node back into their respective site OR deleting the empty site.
Option 2:
Install a local coordinator in the target foreign forest instead of deploying a foreign forest agent.