I've just updated from 7.57 to 7.59 (so no idea if this issue was already present since 7.58 or not).
My situation is as follows: I leave the computer running 24/7 and also mIRC. I am also in a permanent DCC Chat with an Eggdrop, so every time I restart the computer and/or mIRC, I start a DCC Chat with this Eggdrop. This Eggdrop is running on the local network which is a NAT'ed network (with properly forwarded ports at the router) and so has an internal IP address. I also need to be able to DCC Chat (or send) to external publicly routable IP addresses.
So, in the settings in Connect->Local I leave the IP address set to my external IP so the NAT traversal works when wanting to connect to external addresses. But as I said, I'm also in permanent DCC Chat with this one locally running Eggdrop bot, so, upon starting mIRC and connecting to IRC, I go to Connect->Local, change the IP to my internal IP address of the computer running mIRC, open the DCC Chat with this Eggdrop and then once the chat is established I go back to the settings and change the IP back to my external IP so that everything continues to work afterwards for external connections.
Now here comes the issue: These settings don't take anymore since the update. I change the IP address and press OK to close the dialog window but its still set to the IP that was originally filled in... it simply wont take the change anymore whereas before this was never an issue.
In the meantime I thankfully found a workaround, which is to run simply "/localinfo" with no parameters, this changes the IP to my internal one, I do the DCC Chat and then I run "/localinfo <my-external-ip>" so that DCC Chatting to external bots work too.
Should you wonder why I'm doing it this way, its because of NAT timeouts that happen if I just simply leave it set to my external IP to connect to the locally running bot, the connection dies after a while and doing this prevents that and also prevents the connection from needing to pass through the router (which for this bot is absolutely unnecessary), which is also nice.