Question : The home directory drive mapping works and sometimes it doesn't.  What can be causing this instability?

The drive mappings from the logon script is stable.  However, the drive mapping to the home directory is unstable.  Sometimes it doesn't map.  It is called from the account property of the user where the drive is selected and mapped to \\server\share\username.

Answer : The home directory drive mapping works and sometimes it doesn't.  What can be causing this instability?

try mapping it to \\server.domain.local\share\username ? Using the FQDN can help...