This might happen because the datalogger clock is being adjusted by a remote time source. If this occurs close to the same time that the datalogger is due to store data, it can result in either a skipped record or an additional record of data.
If LoggerNet 4 is used to collect data on a schedule, check the setup for that datalogger. Look at the settings on the Clock tab in the LoggerNet Setup Screen. If that is enabled, the clock is checked and set at midnight every day and may interfere with data collection at that same time.
Skipped scans and power outages could also result in records missing from a data table. Check the datalogger’s station status or Status table and look for skipped scans, watchdogs, and low 12 V counts.