Between 09:00 and 09:50 UTC REST API queries for historical data were missing the past hour's worth of data due to an issue when writing the data to disk. The source data wasn't impacted i.e. there was no data loss. Full functionality has now been restored. We apologise for any inconvenience this may have caused. If you have any further questions, please contact us via https://www.bitmex.com/app/support/contact.