In the BI connector, we invoke mongorestore as shown here. Occasionally, mongorestore will hang when we attempt to restore a .bson.gz file using this code. Currently, the hang is only manifesting itself on Windows, and it occurs only sporadically.
We originally observed this hang using an older version of mongo-tools, but it persisted even after revendoring to 4da3a69c46185fb20be26e40064c5d0a5647fde6 (master as of 8/18/17). I have so far been unable to reproduce the hang on a spawnhost, but it does appear to hang in the same location every time (see a log here), when restoring bigobjarray.bson.gz.