I have a 2014 521 C and took it in to have tires, breaks and hubs checked. All was good but my back inside tread of tire was worn down... I just replaced all four tires last July. I had him replace the tire and after a few 100 mile trips, the same tire is showing wear. I am assuming this is an alignment problem...Am I correct or is it something else? Who does work on these type of trailers?