NOTE: This is just a specific way the issue can manifest, collation is not the only setting that can be changed. Take a set of measurements with values 1, 3, and 10. Sorted lexicographically, the order is 1, 10, 3. Sorted numerically, the order is 1, 3, 10. If these measurements were prepared on a collection with the collation setting numericOrdering: false, the control field is min: 1 and max: 3 . Suppose that after preparing the insert but before writing it, the collection is dropped and recreated with collation numericOrdering: true . The insert proceeds normally, making the control field no longer match the data. With numericOrdering: true , the bucket's control.max being 3 hides the presence of the 10 measurement. A subsequent query filtered on value: $gte: 5 would not return the correct data. Reproduction on master: Attached is a patch that will demonstrate the above case. Because validation can detect the inconsistency between the data and control fields on a bucket, the test appears to fail. To get around this, the test will print BUG-97488 if the incorrect behavior is present. Reproduction on 8.0: The same as above, but replace the fail point used in the script with hangTimeseriesInsertBeforeWrite .