A review toggle could wipe every review
Toggling one row's status read the use case's review file, changed one key and saved. If that read failed for any reason, the code treated it as “no reviews yet” and saved a nearly empty file over all of them.
Only a true 404 starts empty. Any other read error propagates and nothing is written. The write is conditional on the version that was read, and the UI shows the reviewer the server actually saved.