Every now and then we run into errors like these :

Fri Aug 10 11:29:38 [Balancer] moveChunk result:

{ errmsg: "can't find index in storeCurrentLocs", ok: 0.0 }

Fri Aug 10 11:29:38 [Balancer] balancer move failed:

{ errmsg: "can't find index in storeCurrentLocs", ok: 0.0 }

On top of that my config.mongos collection is slowly filling up with documents so those are not cleaned up (should they be?). For example I see 71 documents there while there are 20 mongos connected currently.

Any idea what can cause these sorts of issues? Can killing mongos processes cause this for example?