Reproducible deterministically. After a bit the load is run on the primary rs.status() will report optimeDate on any of the secondary being far behind the one of the primary. Can be reproduced even with a 3-members replica set all in the same availability zone, in an AWS datacenter.

Get linkbench from https://github.com/dcci/linkbench and run

./bin/linkbench -c config/LinkConfigMongoDb.properties -l

Relevant configuration bits into LinkConfigMongodb.properties

loaders = 3

or higher