Until recently I have experienced extremely erratic SG values in the first 24 hours after inserting a new sensor when compared to meter BG values. In many cases the difference is over 100 points and not due to exercise/food/insulin activity. Its very, very frustrating as you cannot trust the sensor at all until it settles.
What I found on another forum for 670G users is a concept that they call “marinating the sensor”. What you do is insert the sensor (while the current on is still working and attached to the transmitter) and let the new sensor “marinate” for several hours. For instance, if you are going to need to change the sensor say, Tuesday morning, insert a new sensor Monday evening before bed - tape it down and protect the connector with something like a band aid. Leave the transmitter on the current one. On Tuesday morning charge the transmitter and then connect it to the sensor you inserted the evening before.
I have had really good results with this technique. The erratic sensor value behavior has cleared up and I am able to go into directly back into auto without having to be in manual mode for several hours while the sensor settles down. I generally get a 6 hour calibration on the first calibration rather than 3 hours. Some people have also reported very short warm-up times (Iike 10 minutes). I didn’t get that lucky but I am really happy with getting rid of the erratic sensor behavior and not having to wait to get back into auto.
Don’t know if anyone else is dealing with the erratic sensor values, but it’s a technique to consider.