If you're using /sockopen on an ipv4 domain name from a /server -6 connection, -6 completely disables ipv4 for that connection, what's the error message you get?
The -4 switch is there to force ipv4 back in this case, so it's normal.
To get ipv4 to work, you need to use the ipv6 setting which gives priority to ipv6 without disabling ipv4 (use global mode and stop using the -6 switch in /server):
https://en.wikichip.org/wiki/mirc/ipv6