If a template field's value shows %20 where you'd expect a space, this is expected behaviour, not a bug.
The field has the Urlize option enabled. Urlize encodes the field's output so it can be safely used inside a web link, for example a tracking URL. Since a URL can't contain a literal space, it's encoded as %20 instead.
For example, Summer Sale EMEA becomes Summer%20Sale%20EMEA.
If you'd rather see readable spaces, you have two options:
Turn off Urlize, or
Use the Replace whitespaces option to swap spaces for a character such as a hyphen or underscore instead.
Learn more about these settings in Template Fields.