I'm a longtime GNU Emacs and macOS (and GNU Emacs on macOS) user, on a US Gov't owned MacBook Pro (16-inch, 2019) running macOS 11.6.3 (Big Sur).
For the last few weeks, GUI versions of Emacs are acting as if the Control or Meta key was being held down for a few seconds after it was released. Needless to say, this makes editing particularly painful.
This has happened with both the MacPorts and emacsformacosx dot com builds of Emacs 28.1, and with older Emacsen running in Linux virtual machines!
Emacs running in the macOS Terminal app is not affected.
The problem does not affect other Mac apps, unless I am switching context from Emacs to some other app.
Does this sound familiar to anyone? How can I chase down the cause of this problem?