A page name is subject to a few rules because it passes through our servers via the HTTP protocol. If you do not follow our recommendations, it is highly possible that the page parameter will never be collected and, moreover, it will block the rest of the hit.
If you want to use the "#" character in a page name you will need to encode it in UTF-8 format, otherwise, it will erase everything after this character. So to use a #, you need to replace it with %23.