OK long time lurker, first post and bug report(of sorts?).
I am on latest version of mirc on Windows 10(insider program, latest build 10240). I notice now if lets say you have 3 different servers running with lets say 1 channel open on each server. If you click channel on server A, then click channel on server B then click on channel in server C. If you click server A again, it goes back to that channel, but if you click channel on server A again it goes to channel on server B even though the last channel you clicked on was channel in server C. Same thing happens if you click channel on server C again, takes you to channel on server C but if the same channel(server C) is clicked again it goes to channel on server B. I used to use this fine so I just quickly go back and forth between 2 of my favorite(main) channels. Not sure if this is a bug or not, I just know it worked before with last version on this same PC and windows version. Hope I helped out. Thanks!