Just an FYI if anyone is having trouble with their GrovePi+ giving incorrect information from sensors, check the firmware.
I was trying to use the ultrasonic sensor and getting all sorts of incorrect values. I was also experiencing delays and, oddly, the curosr was resetting to the bottom right corner.
Checking the firmware of the GrovePi+ returned “firmware version 156.46.28”
The real firmware was supposed to be 1.4.0.
To check the firmware: GrovePi/Software/Python/grove_firmware_version_check.py
to update the firmware https://www.dexterindustries.com/GrovePi/get-started-with-the-grovepi/updating-firmware/
After updating all of my data from the ultrasonic ranger sensor is working properly.