The solution was much simpler than expected.
In the krb5.ini file, we replaced the kdc from the servername to the ip-address and then it worked...
the krb5.ini looks now as follows
libdefaults]
default_realm = TEST.DOMAIN
dns_lookup_kdc = true
dns_lookup_realm = true
default_tgs_enctypes = rc4-hmac
default_tkt_enctypes = rc4-hmac
[realms]
TEST.DOMAIN = {
KDC = 192.168.7.XX
DEFAULT_DOMAIN = TEST.DOMAIN
}