This sounds very odd. Can you guys each tell me your phones make and model?
I'd like for you guys to also try a 3rd party app that uses the standard APIs. Even before Mango shipped, OEMs like HTC were able to use their own proprietary APIs for accessing the compass. HTCs compass app could still be doing that today.
Can you please download and try a 3rd party compass app? I'm a fan of "Jack of Tools" because it tells you when your device needs calibration and also an alternative way of calibrating it different from the "figure 8". The figure 8 wasn't working on my HTC
but the alternative method (slow panorma) did.
Jack of Tools can be found here:
They have an exceptional FAQ about using the compass here:
Definately check out that FAQ and see if it helps at all. If the compass seems to be working correctly in JoT but not in GART, I'll try to get it fixed in GART. If it's not working correctly in JoT
then I can ask our internal forums if it's a known issue or if it's being worked on. But again, I'll need your make and model for that.