We have had our bike for 6 months and two of us ride almost every day. I recently noticed a noise coming from the wheel that I don't think I heard before. It isn't loud, but is a "creaky" noise. I looked at the magnets and they are not rubbing anything. The noise is the same no matter the cadence or the resistance. Do you have any suggestions of what it could be? We are not handy or mechanical, so won't be able to do any DIY repairs.