That’s what the data looks like when the CTD sensor gets disconnected from the Mayfly. The turbidity sensor is still being read, and there was no change in turbidity around the time of the data loss. So you can rule out someone stealing the sensors, or that it was damaged during a flood event, since there doesn’t seem to be an event happening. And since it was at 2am, it’s unlikely that someone is there unplugging things. My guess is that a mouse chewed into the cable between the station and the water, or that it’s a random (but really rare) electrical failure of the sensor. Which station is this from? Have you been to the site to check on the condition of the cables?