I am unsure if this is known, or how it could have been missed, but typing Cmd+Shift+Z will run the Undo function instead of the Redo on a mac. Thus you cannot do a redo. I’ve tested it on the main editor on the homepage of Prosemirror.net. I swear it used to work. This is happening on Chrome and Firefox, so I assume everywhere else.
Did we break the keymap handling recently to treat a Cmd+Shift+Z as a Cmd+Z?