Segfault on drop of source collection during MapReduce

Mongod process seems to sporadically causing segment errors while running mongo aggregation framework or/and right after completing the aggregation pipeline, most notably during dropping temp collections created as part of the aggregation framework.

We run aggregation on multiple keys on a collection, we need unique counts for each of the field values, several aggregation pipelines are run in parallel and target collections are dropped after reading the results and writing the outputs to a unified collection [ done via map-reduce framework].

The errors seem to be happening quite frequently - in dev and qa.

Platform specs : Mongo Db version 3.2.1
Storage Engine: WiredTiger
OS :Linux version 3.13.0-74-generic (buildd@lcy01-07) (gcc version 4.8.2 (Ubuntu 4.8.2-19ubuntu1) )