bug#49991: 27.2; Anomalous Key Translation

[Robert Morelli]

From time to time, A-c, A-x, and perhaps a few other similar keys

sequences, stop working and become self-insert-command.

This seems to happen after running the command

C-x 8 <any key>

where <any key> is any key at all, not just c.

For what it's worth, my iso-transl-char-map and iso-transl-char-map 
variables contain pairs like

("*c" . [162]) ("c" . [162])

I don't use this feature much and I only know this from occasionally 
hitting this sequence by accident.

I am working on a MacBook Pro laptop running Mac OS 10.5.1.In my 
init.el, I have the following:

(global-set-key (kbd "A-c") 'kill-ring-save)
(global-set-key (kbd "A-x") 'kill-region)
(setq mac-command-modifier 'alt) ; cmd key -> alt A-
(setq mac-option-modifier 'meta) ; option/alt key -> meta M-
(setq mac-control-modifier 'control) ; control key -> control C-
(setq mac-function-modifier 'super) ; Fn key -> super s-
(setq mac-right-command-modifier 'hyper) ; right cmd key -> hyper H-

so the key sequence is invoked with the physical Apple command key.

When I run describe-key on, say, A-c, I get:
¢ (translated from A-c) runs the command self-insert-command (found in 
global-map), which is an interactive built-in function in
‘src/cmds.c’.

It is bound to many ordinary text characters.

(self-insert-command N &optional C)

Probably introduced at or before Emacs version 22.1.
...

This behavior is unexpected and unwanted. After the sequence changes, 
re-evaluating

(global-set-key (kbd "A-c") 'kill-ring-save)
produces no error message, but has no effect. I have not been able to
find any way to get the binding to return to normal except by restarting 
Emacs.





In GNU Emacs 27.2 (build 1, x86_64-apple-darwin18.7.0, NS appkit-1671.60 
Version 10.14.6 (Build 18G95))
of 2021-03-27 built on builder10-14.porkrind.org
Windowing system distributor 'Apple', version 10.3.2022
System Description: macOS 11.5.1

Recent messages:
¢ is undefined
<mouse-3> is undefined
Saving file /Users/robertmorelli/MyCloud/Info/Notes/EmacsNotes.tex...
Wrote /Users/robertmorelli/MyCloud/Info/Notes/EmacsNotes.tex
Saving file /Users/robertmorelli/Library/Mobile 
Documents/com~apple~CloudDocs/MyCloud/Info/Notes/MacNotes.tex...
Wrote /Users/robertmorelli/Library/Mobile 
Documents/com~apple~CloudDocs/MyCloud/Info/Notes/MacNotes.tex
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Configured using:
'configure --with-ns '--enable-locallisppath=/Library/Application
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Important settings:
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Load-path shadows:
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