Don't know if problem has gone, checked with the latest release (and attached settings) and got the following output in jobs:
$ /usr/bin/hg clone --noupdate https:abort: http authorization required for https:ERROR: Failed to clone https:Master cache lock released.
ERROR: Could not use caches, not fetching branch heads
ERROR: No version feature/RT462020-docker-compose-research found for library ci
org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
WorkflowScript: Loading libraries failed
Worked fine to me on 1.61 version of mercurial plugin.