We just found that the BME280 Bosch datasheet states that CSB and Vddio must be connected! See the ‘notes’ in this screenshot:
But most (if not all?) breakouts (like DFRobot and Adafruit) leave it floating (see https://learn.adafruit.com/adafruit-bme280-humidity-barometric-pressure-temperature-sensor-breakout/downloads)
We are testing it out but this could be the issue which causes it to be unreliable… or am I missing something? 