I have written a python driver interfacing to the BME280 via the bus pirate logic analyser. Temp and humidity values appear "believable" (they may be off a bit but we're talking a few percentage points at most). Pressure values, however, are much too high - I am reading north of 151229 Pa. Three different BME280 sensors on 3 different boards all read and behave the same with T and HR fine/in range and P reading much too high. I've used the Bosch spreadsheet to verify the compensation method and when i feed in the value I am reading from the bulk measurement as well as the calibration factors, the spreadsheet agrees with my own computed value. Yet, 150K Pa is much too high. It seems the raw pressure value is off but that is hard to explain if all 3 sensors are off similarly.
p1 0x9373
p2 0x-2997
p3 0xbd0
p4 0x20c2
p5 0x-18
p6 0x-7
p7 0x26ac
p8 0x-27f6
p9 0x10bd
Raw pressure: 0x170