If one DA user account has 1 or more domains, and the default domain is deleted the default domain is not changed automatically to a different domain. Instead is used the old one.
If i am trying to resend from reseller level the password for that account is still saying me the domain of this account is the old domain (no longer on domains list) instead of one of the newer domains.
CHeck the /usr/local/directadmin/data/users/username/user.conf for that user. There is a field:
domain=domain.com
If that's the field you're referring to.. when I tested on our build systems, DA did set it to the last remaining domain.. so if we're getting different results, I must be doing something different than what you're doing..