Reproduction for meteor/meteor#9619.
git clone https://github.com/hwillson/meteor-issue-9619.git
cd meteor-issue-9619
meteor npm i
meteor
Go to http://localhost:3000 and watch your server console for:
Exception in defer callback: Error: The Mongo server and the Meteor query disagree on how many documents match your query. Maybe it is hitting a Mongo edge case? The query is: {}