Upper chunk key is not written correctly to the log. In src/monog/s/balancer_policy.cpp the min key is written as the max key and in src/mongo/s/d_split.cpp the max key is missing, only the label "max" is written.

https://github.com/mongodb/mongo/blob/master/src/mongo/s/balancer_policy.cpp#L450
https://github.com/mongodb/mongo/blob/master/src/mongo/s/d_split.cpp#L477

These errors makes it difficult to diagnose shard problems.