[This is on a non-sharded 8.0 replica set]

We store fairly large, schema-less data structures in time series collections. A job runs once an hour that deletes docs older than X time. Several times a day, we receive a "mixed schema" error when the job attempts to delete certain docs from a time series bucket:

Cannot write time-series bucket containing mixed schema data, please run collMod with timeseriesBucketsMayHaveMixedSchemaData and retry your update 

We isolated our investigation to a single bucket to see if we could reproduce the error and find its source. The bucket contained 10 documents, and we discovered that the seventh doc was causing the problem: `Jungle.Anvil.Quiet.Wheat` (in the attached anonymized data) was an array of `null` values, while in the other docs that contained `Jungle.Anvil.Quiet.Wheat`, it was an array of numbers. We tested by changing the `null` values to numbers and found that we were able to delete any docs in the bucket successfully.