Hi there,
Good stuff for sure.
the IMU temp is a little , funny I have found. based on where the IMU is under the LID.
more of an internal reading IMO, I use it just to see if the hardware is alive.
The examples show the delay as well , I believe it is needed between readings for settle time.
NOT ideal but add some delay to test if it is the effect I think it is.
HTH
GL 
PJ
also I like the Nrf_dongle for $9 bucs make BLE testing and trouble shooting a breeze the NRF_connect for desktop is the truth IMO.