Sounds like its rusted up. Had the same with mine sent back to cannondale in Holland, repaired and charged even though the bike was only 5 months old. Apparently one shouldnt ride in the rain or through puddles, according to Cannondale. Not the Magura version though.
Needless to say I flogged the thing and got a proper bike. I didnt pay either, gave Evans loads of flack, not fit for purpose and all that and they settled the bill. Needless to say I will not be supporting that brand again.