Delete key used to work...but now...

My delete key used to delete backwards all by itself. But now I have to used Shift-Delete, or Control-Delete or Option-Delete with it to get it to delete letters in any word processing document like this.

What did I accidentally do?

(Using latest Sierra, and recently upgraded the Numbers/Keynote/Pages group)

It looks like from my research that the delete key was never supposed to work all by itself to delete backwards. But mine did until sometime this morning.

 

And now, a week later after the delete key spontaneously, changed to require a modifier key to work, it is back to being a back delete key again. Now that I have gotten used to automatically using shift-delete to delete backwards, just Delete works again too.

I wish I knew. I did restart the system a few times. Maybe it was a need for a restart that did it. I can't believe it would have been something that simple.