mIRC beta v7.65.563 - Windows 8.1 Enterprise x64 - Today I also saw and caught such a bug. I just leave it here for you to know. In the screenshot, the locations are marked with red arrows:

[Linked Image from i.ibb.co]
It is extremely difficult to determine the cause of this bug. This is the second time this has happened during beta testing. I have not used a remote desktop or remote computer. Not this time, anyway.
If this help to localize the problem, then I have was open at the same time 2 mIRC clients from different independent folders. The client was in a minimized state while I was working in Photoshop.

All icons are clickable, but their dropdown menu has different list of items:

         [Linked Image from i.ibb.co]

In the client "mIRC v7.63" this has never did not have. Bug probably appeared in later versions. This bug is quite rare is not essential and easy to fix (by switching off and on the Menubar), but it can mislead what to click on.

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