CCS installation is at version 11.1 with PU 2015-2 (or lower) and SCU 2015-3 (or lower). When you try to configure domain cache credentials for domains having the same short, netbios names CCS will state that the second one cannot be created because there is already one with that name in existence.
Domain cache credentials for domain XX already exist.
CCS matches on the netbios name of the domain when looking for the correct domain cache credentials to use during a Windows data collection.
This solution applies to CCS version 11.1 at PU 2015-2 and SCU 2015-3 only. You must be at this code level to apply these fixes.
Apply Quick Fixes 10211 and 10501 (see attachments). Both Quick Fixes must be applied to obtain a new functionality that enables users to select which assets fall under which set of domain cache credentials.