Incomplete and differing keyboard shortcuts with tmm-prompt, depending on filetype

[Tim Johnson]

GNU Emacs 28.2 (build 2, x86_64-pc-linux-gnu, GTK+ Version 3.24.20, 
cairo version 1.16.0)


When I invoke tmm-prompt with a list of files as the menu argument, the 
keyboard shortcuts
differ depending on the file extension of the buffer visited by the 
current window. If the file
extension of the visited buffer is .el, there is an alphabetic keyboard 
shortcut for every item.

If the file extension is .c, .h or .txt, menu items are marked by 
numbers, up to the point where
all numbers are used and those following have no shortcut.

I am curious as to the reason. The function call invoking tmm-prompt has 
no optional arguments.
Example: (setq menu (append menu (list items)))

Thanks

--
Tim
thjmmj15@gmail.com