works as expected UNLESS it encounters a nonbreaking space in a Note followed by a nonbreaking space (immediately outside the Note) — in which case it deletes the character following the second nonbreaking space.
For example, this shows the text before running the script:
In this case I typed "This is a test." twice. Then inserted two nonbreaking spaces between "a" and "test". Then in the first instance I selected the first nonbreaking space and converted it to a Note.
Then I ran the Find/Change.
This is the result:
The routine properly changed both nonbreaking spaces to spaces in the second sentence.
But in the first sentence (with the Note) it converted both nonbreaking spaces to spaces but also added an extra space (hard to see immediately next to the Note symbol) and deleted the "t" in "test".
This is repeatable with any text as far as I can tell.
IMPORTANT NOTE: This only seems to happen if you select "Change All" in the dialog. If you instead choose Change/Find and step through it doesn't delete anything.