This might happen because the data logger clock is being adjusted by a remote time source. If this occurs close to the same time that the data logger 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 data logger. 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 data logger’s station status or Status table and look for skipped scans, watchdogs, and low 12 V counts.