Steps to reproduce:

• Create an EF Entity with a List of objects, containing a List of objects
• Create your matching MongoDB database and setup your database connection (you can actually get away with a valid connection string only to repro the issue)
• Write a Linq or Lambda expression to query the Entity, on any of its members, _id will work
• Query causes invalid operation exception to be thrown

Notes:

Minimal repro here: https://github.com/seannybgoode/MongoEFCoreListsBugDemo/tree/master

Worked with Damien Guard on this, and he assessed that this is separate from EF-63