Mongo Divide limit exceeded while mapreduce function is called

I tested a map operation on a huge dataset of about 25 million documents. The shrink function is correct and works great when testing on a small dataset.

I am getting the following error when running mapreduce over a large set

"errmsg" : "exception: Exceeded depth limit of 150 when converting js object to BSON. Do you have a cycle?",
"code" : 17279,
"ok" : 0