Not the grove Pi, but the Raspberry Pi itself is flawed. . .
Are you using the i2c port or the software i2c via AD1?
There is a known bug with hardware i2c on the Raspberry Pi, where they don’t implement clock-stretching properly.
The issue is that some sensors, (maybe yours too?), are sensitive to the accuracy of the i2c implementation. If it’s not dead-on spec, the sensor does weird things. Since it appears that the people who implemented the i2c hardware solution used on the Pi kinda’ waved at the spec as they drove by, it’s a bit squiffy and the hardware i2c suffers as a result.
The Dexter “software” i2c driver solves these problems since it implements the i2c spec more accurately than the Raspberry Pi’s hardware. The down-side of this is that their software solution uses one of the two A/D ports, leaving you with only one left.
You might want to search around here about that - there are a number of articles, especially about the IMU sensor, that discuss this problem in detail.
Thanks for an excellent question and don’t forget to write back and tell us what happened!