There is a scenario where we are running with the changes to durable history when we write a value to the data file with a stop timestamp (if it's removed, but the remove isn't globally visible).

If a user then starts using that database with MongoDB 4.2, I believe we ignore timestamps altogether, and thus the value will become visible again on startup.

While writing this up, I've realised that rollback_to_stable on clean shutdown might fix this up - but we should confirm with testing in the least.