Instances can end up with multiple `ApplicationSetting` records when Redis is down

A couple of times recently, I've noticed that some instances have multiple ApplicationSetting records in the database. If you inspect ApplicationSetting.first you may see drastically different settings that ApplicationSetting.last. Luckily, I think we mostly use ApplicationSetting.last in code so we're fairly consistent. But the question is, how are they getting multiple records here?

@DouweM Any ideas how this would happen or if we can/should do anything to prevent it?