Using mIRC Beta 7.64.6394 on Windows 10 Home, I have encountered a new issue since your last change to try to fix the error reported in this thread. Somehow, I see the buttons twice now when windows are maximized, and if I put the windows into windowed mode inside mirc, a phantom set of buttons that do nothing remain at the top.
These 'phantom buttons' do nothing when a window isn't maximized inside of mIRC, but they do when a window is maximized.
Edit 1: Does not happen til I join a channel/open a second window, but persists after I close all but the first status window. Tried on a fresh copy of the beta as well as the client I normally use.