DNS Cache module does not seems to handle properly DNS SRV records.
Opensips "dns cache" perform a lookup on mydomain.com.
The DNS answers : SRV gw1.mydomain.com and gw2.mydomain.com
Then Opensips perform an "A" query to "gw1.mydomain.com"
The DNS answers 220.127.116.11 for gw1.mydomain.com.
Finaly opensips forward the SIP request to 18.104.22.168
After that, on a new SIP request, Opensips continue to forward request directly to 22.214.171.124 (gw1.mydomain.com) and never trie to use gw2.mydomain.com
In my point of view, there is an issue in the DNS Cache module. Opensips should try randomly both mydomain.com SRV records gw1.mydomain.com and gw2.mydomain.com