Home directory moves itself to a different domain controller

The home directory of some of our users are randomly and sporadically moving without manual intervention from one DC to another DC. Both DC’s are running windows 2000 advanced server. The DC are on different LAN’s connected via the WAN.

The users drives are mapped via script at login to drive letter “M”
The path \\servername\user$\%username%
All client PC’s: XP

The folder must be manually moved back to the correct DC.

Any thoughts on why this is occurring and how to fix it?