That's the redo command

In most other programs, it's command-Z, command-Y. I tried adding the shift, but that doesn't work either. Oh well. Thanks for the suggestion!

But it will work every time:
Let's say you typed then "undid" the phrase "l screwed up." (Without the quotes)

First, press and hold the cap key and type the letter I. Release the cap key. Then hit the space key. Then hit the s key, then the c key, then the r key, then the w key, etc etc etc.

To avoid this in the future, avoid the command-y key combo.

You're welcome.

But seem to remember Cmd + Y being the combo for 'Redo'.