On at least PMM 1.0.5 and greater the following error appears on MongoDB 3.2 clusters after 3.2.10 when using SCCC/mirrored config servers:
This causes some queries in the mongodb_exporter to also fail. This is due to this MongoDB bug: https://jira.mongodb.org/browse/SERVER-27864
A workaround to this issue has been created in percona/mongodb_exporter pull-request: https://github.com/percona/mongodb_exporter/pull/53.
This ticket is to publicly track a fix for this problem.