[1] Search in Calibre to see what happens when you search on one and then the other, and whether both capitalizations always appear together.
[2] There are simple quotes and there are fancy quotes. They are totally different characters. I would do a search & replace of your Tags to replace all fancy quotes with simple quotes so you return some sanity to your Tags.
For example:
https://www.cl.cam.ac.uk/~mgk25/ucs/quotes.html