SAMBA - Problem modifying SID using pdbedit

After changing the SID of any account, eg:

pdbedit -U S-1-5-21-2411803954-1159576741-3064619986-500 -u administrator -r

...the SID *is* changed successfully, but I get the following error:

| Unable to modify TDB passwd ! Error: Record does not exist
|  occured while storing the RID index (RID_000001f4)
| Unable to modify entry!

From this point whenever I try to change the password using smbpasswd, I get a similar error to that above.

Using pdbedit -x to remove the account gives the error "Unable to delete user <user>", but pdbedit -L doesn't list the account any more.

Using tdbdump I find there is a remnant left over in passdb.tdb.  Eg:

{
key(13) = "RID_00000bbc\00"
data(5) = "test\00"
}
{
key(13) = "INFO/version\00"
data(4) = "\02\00\00\00"
}

This problem only happens after changing the SID on an account.

Many thanks,
Steve :)