DVCS connector is not passing value for pagelength properly if it is not set causing DVCS Connector can no longer fetch pull requests. It tries to make the following call during synchronization:

https://bitbucket.org/!api/2.0/repositories/[username]/[repoName]/pullrequests/[prNumber]/comments?pagelen=0

Which returns a 400 bad request with the message that the value for pagelen is invalid. Changing the value to something greater than 0 works.