src/main/java/com/atlassian/bitbucket/jenkins/internal/http/HttpRequestExecutorImpl.java generates a string that is then placed in the User-Agent header field of HTTP requests:

            bbJenkinsUserAgent = "Bitbucket Jenkins Integration/" + version;

According to the specification of the User-Agent header field in RFC 7231 and the definition of token in RFC 7230, a product identifier cannot contain space characters. As the string is apparently intended to contain only one product identifier rather than three, it should instead be something like "Bitbucket-Jenkins-Integration/" + version.