ssh_exchange_identification: read: Connection reset by peer

We have many Jenkins jobs talking to bitbucket server using one ssh key, and we are seeing this below error more and more recently. Can you please suggest what's cause and solution?

Thank you!
Steven

Loading library mule-shared-library@develop
Attempting to resolve develop from remote references...

/usr/bin/git --version # timeout=10

using GIT_SSH to set credentials
/usr/bin/git ls-remote -h -t git@bitbucket.org:isagenix/mule-jenkins-shared-lib.git # timeout=10
hudson.plugins.git.GitException: Command "/usr/bin/git ls-remote -h -t git@bitbucket.org:isagenix/mule-jenkins-shared-lib.git" returned status code 128:
stdout:
stderr: ssh_exchange_identification: read: Connection reset by peer
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.