I have a really weird error happening sometimes in one of my background jobs. The stack trace I got (the Mongoid-related part) is:

NoMethodError: undefined method `clear' for true:TrueClass
.../mongoid-2.0.0/lib/mongoid/attributes/processing.rb:122
.../mongoid-2.0.0/lib/mongoid/attributes/processing.rb:28
.../mongoid-2.0.0/lib/mongoid/document.rb:142

This happened 3 times over a few days, with hundreds of thousands of other similar jobs completing successfully during that time. I can't reproduce it locally on the same data and I can't see any patterns in the inputs or the time when it happens.

The line of code that runs just before this error is simply Profile.new. From what I can see in the Mongoid code, the methods it runs afterwards iterate over two internal hashes, and then suddenly one of these hashes becomes a boolean true value, which doesn't make any sense to me.

Any ideas?...