I occasionally see this output:

MongoError: Incorrect arguments
at Object.toError (/home/admin/idlebot/src/modules/idle/node_modules/mongodb/lib/mongodb/utils.js:114:11)
at Server.Base._callHandler (/home/admin/idlebot/src/modules/idle/node_modules/mongodb/lib/mongodb/connection/base.js:455:65)
at /home/admin/idlebot/src/modules/idle/node_modules/mongodb/lib/mongodb/connection/server.js:481:18
at [object Object].MongoReply.parseBody (/home/admin/idlebot/src/modules/idle/node_modules/mongodb/lib/mongodb/responses/mongo_reply.js:68:5)
at [object Object].<anonymous> (/home/admin/idlebot/src/modules/idle/node_modules/mongodb/lib/mongodb/connection/server.js:439:20)
at [object Object].emit (events.js:95:17)
at [object Object].<anonymous> (/home/admin/idlebot/src/modules/idle/node_modules/mongodb/lib/mongodb/connection/connection_pool.js:201:13)
at [object Object].emit (events.js:98:17)
at Socket.<anonymous> (/home/admin/idlebot/src/modules/idle/node_modules/mongodb/lib/mongodb/connection/connection.js:440:22)
at Socket.emit (events.js:95:17)
at Socket.<anonymous> (_stream_readable.js:764:14)
at Socket.emit (events.js:92:17)
at emitReadable_ (_stream_readable.js:426:10)
at emitReadable (_stream_readable.js:422:5)
at readableAddChunk (_stream_readable.js:165:9)
at Socket.Readable.push (_stream_readable.js:127:10)
at TCP.onread (net.js:528:21)

It's very unhelpful, and nothing in the stack trace points to anything in my code. How can I debug where and why this is happening?