Frank,
The DotBox has the MPL3115A2 pressure/temp sensor. Here’s the datasheet:
http://www.nxp.com/assets/documents/data/en/data-sheets/MPL3115A2.pdf
The temp accuracy is +-1C @ 25C and +-3C for the whole range. This will account for some of the variation you see. The rest can likely be accounted for by the fact that the sensor is inside the box – the LoRa radio generates a lot of heat when it’s in TX and RX mode especially.
Hope this helps!
Cheers,
Mike