mongos on all servers crash when adding an index

I'm trying to add an index on a largish (~100 GB) and busy collection (many servers connecting, hundreds requests per second):

db.screenshots.createIndex(

Unknown macro: {"user_id"}

,

Unknown macro: {"unique"}

,

Unknown macro: {background}

);

db.screenshots.createIndex(

Unknown macro: {"deleted"}

,

Unknown macro: {"unique"}

,

Unknown macro: {background}

);

It seems to work, but unfortunately after the index is built, all mongos instances on all servers crash (to be precise - around 90% of mongos processes crashed; the ones which didn't crash were on idle servers with few connections).

We are using mongo 3.2.13 on Ubuntu 16.04, with sharding and replication, and mongos connecting.

See the attached log with a crash.