There is a bug described in SERVER-50971 where MongoDB observes a record, and in the same snapshot, reads the record again, but WiredTiger returns WT_NOTFOUND.

Consider adding a "double-check" behavior to collection validation. This would lookup a record immediately after validating it. We may not want to enable this by default due to the amount of extra work, but we could enable this in many of our tests.

The hope is that this extra coverage would uncover similar isolation bugs in the future.