same for me after upgrading to Tahoe 26.1.

"Internal inconsistency in menus" errors have appeared upon starting my macOS application. This happened as soon as I upgraded to Tahoe 26.1. My app is not using any custom classes in the menu. This appears to be a bug related to Tahoe.

I experience the same issue. First time I saw this error was when I installed XCode 26.0.1 I suspect this is a bug in Xcode as the error seems to relate to something in different framework.

6 years on and the silence is still deafening. I notice that NSMatrix is not depreciated as yet, it is only "discouraged in apps that run in macOS 10.8" (https://developer.apple.com/documentation/appkit/nsmatrix)

Using XCode 12.3, changing the Size parameter on Toolbar item from Explicit to Automatic fixes the error.