I'm on my fourth or fifth new type, 15 day, Freestyle Libre 2 and it seems to be need to self-calibrate much more often than the previous 14 day one. It also seems to over-shoot changes, then readjust, more than the previous type too. So I'll go shooting down and look as though I'm going low, so I go for a fingerpick to double check and by the time I've done that the sensor has completely changed its mind and decided that I never left the green zone.