Can you please give us some more context about the call you are making? Is this a trigger or a REST API. If a REST API, what version? Also, can you send the complete request body?
You are most likely receiving this error because there is a character in the URL you passed that must be URL encoded. Your best bet is to encode all of the special characters in your URL using this chart using http://vermontdatabase.com/cloudwriter/url_encoding.htm. I see you already did that for the space character by using %20.
The webservice connector should handle encoding of character ootb. I know there was some recent bug because of new functionality added but when I am writing this it should work fine in sandbox without manual encoding. Please provide the url without encoding and see how it works.