Sometimes, created_at gets saved as nil, while the rest of the model gets saved fine. Since created_at is just implemented using a before_create callback, I'm not sure how this could ever happen.

Some thoughts:

• It's only ever happened to one model, which does happen to be my largest collection
• I have another field exclusively set in a before_create filter, and it's never set to nil

Code looks something like this:

m = MyModel.new

# ... lots of mutation & additions to m (embedded & otherwise)

m.touch 
m.save!

Running mongoid 3.1.4 w/ mongodb 2.4.4 in safe mode.

Has anybody else experienced this?