ThomasNelson
Thomas I'm not seeing those screenshots you tried to link to by the way.
But: it sounds like you're having the same problem I did. I think the answer is to:
EITHER change the name of all your daily notes that are single figures from (for example) "5 February" to (for example "05 February"
OR edit the Open Today's Note shortcut so that it uses the date format "d MMMM" (the one provided on the forever Notes site uses dd MMMM I think.
I changed the shortcut to use the the d MMMM date format and mine is working again now.
My assumption (and it is only an assumption) is that this started happening due to some sort of minor change happened in Notes or Shortcuts.