Has anyone here ever had to send a lens back to the manufacturer for re-allignment purposes? In other words, has anyone ever had a problem knocking a lens element out of place after dropping or banging the lens against a hard object by mistake? Any idea if newer autofocus lenses are more susceptible (probably mispelled that) than their older counterparts to become out of allignment due to more use of plastics? On that same note, would it be possible to damage or alter a lenses element allignment if the lens were left in a vehicle on a hot day? I would be curious to know if the heat would deform the lens on a very small scale so that it won't be noticeable at first but in time would get worse. Any experiences with this?