Snapshot capture

Recently I’ve noticed that my hourly snapshot capture time will change randomly in the middle of the night. For example, the entire day previous my hourly snapshot will happen at the 6th minute of every hour (1:06, 2:06, 3:06 etc). In the middle of the night though, the hourly snapshot capture changed to the 26th minute of every hour and has since stayed the same. I’ve tried to look this up previously and have had no luck. I was just wondering if anyone else has noticed this on their snapshots, or if this is a normal thing that the doorbell changes on it’s own.