NOTE: OOOPS - I did this response and used screenshots copy/pasted in, but they didn't save. Edited to add pictures...
Thank you for the response, Neo. Here's what I'm doing:

Note the formula shown in the top right. That's the formula in B1. Now I fill down...I double-click the little box in the lower right corner of the cell, and now I see this:

Note that all values are zero, even the ones that are NOT equal to "abc"
Here you'll see what is in B4 ... note that the formula is correct but not the result in the cell:

I get the same results if I drag down from B1 and then hit Control-D to fill down in that manner. It fails just as it does when I double-click the little square thingy.
Now here's something I discovered later: IF I save the sheet after making the change (which I often do NOT want to do), I see this:

...which is, of course, the desired result. BUT - I don't WANT to save the sheet until I'm satisfied with the results. I don't want to have to save it to see the correct numbers.
This error is consistent. Every sheet I have where I try to fill down (which is something I do virtually every day), it fails like this.
Hopefully this helps...