What kind of lock is it?
How about battery levels? Perhaps at night its cooling is causing a false report. If it happened about a year ago it may be the summer affecting the lock sensor.
I know my Schlage if its not in fully in the lock position, it reports unlocked. I don’t have any random status changes though.
edit: Here is your post from exactly a year ago. I am guessing the weather (heat, cooling at night) is causing the lock to false report. Could reach out to the manufacturer and see if they know anything.