Same as the 'Ampersand bug as is described in "BUG] url with '&' are not correct url? needs a fix" there is a bug with added a URL which has a 'space' character. URL with spaces are automatically generated when you:
-1- copy a link from an Outlook email (and Copy-hyperlink fe.)
-2- use Classic View in SharePoint and then use 'copy link'.
Both cases gives 'Invalid URL' when you paste them in a Planner ticket and do Add-Link. This is quite annoying.