it just depends on where and how one spends your day my friend... i work in the construction industry and probably get more dirty in a day than the average office job worker... any magnet ive ever had on any personal device would end up in need of regular cleaning of metallic debris. Apple just put out specific "debris" cleaning instructions for the magsafe puck for this exact reason and after a week of magsafe use i already have a ring of debris around the edge of the puck.
anyhow, more importantly, and back to the OP... my wireless charging is already broken and im fairly sure its due to using a car magnet.
i have 3 magsafe charging pucks and none of them work anymore. (telling me its the phone and not the puck itself) i had been using the puck in between my phone and my car magnet and for a few days it worked great. i then noticed that if i was to put the phone onto the puck that was already stuck to my car magnet, sometimes it would NOT start charging... this then became the norm and in order to get it to charge i would have to remove both items from the car magnet, disconnect and reconnect the magsafe puck from the phone a couple times to get the charging to start. this worked for a day or so but then it seemed to stop charging after a few minutes of having the two items stuck back to the car magnet. now, none of the pucks charge the phone, regardless of the phone sitting on a desk or a car magnetic holder. Im seeing quite a bit of "magsafe" news from apple lately... whether its guidelines or warnings. looks like the magsafe is turning out to be buggy as ****. damnit
i guess i cant be %100 sure the culprit is the car magnet however, it makes allot of sense that introducing another strong magnet right into the same area that a magnetic inductive system is trying to do its thing would cause a problem.