Consider a member who used many IP addresses to post topics and replies. So, if you see post details in MCP, there are several pages for IP addresses (IP pagination is a new feature for phpBB 3.2.1 and phpBB 3.1.11).
The links '(Look up IP)' beside IPs work only in the first page. If you click on a such link in another page, you switch to the first IP page. The footer link 'Look up all IPs' is also problematic, since it also switchs back to the first IP page.
The only way to look up a IP in another page is copy/paste the link, replace #ip by &start_ips=XX#ip, where XX is used to define a page. I experiment that issue in phpBB 3.2.1, but perhaps it also occurs in phpBB 3.1.11 (I didn't test it).