While taking down my Glock 19 tonight, noticed some strange wear on the rear left slide rail. I've always used light cleaners on this such as Hoppes Elite, nothing that should cause any poly breakdown, and it's never had anything other than factory Winchester rounds through it, total of less than 2000 rounds, cleaned after each session. The wear seems to be the breakdown of the poly behind the rail itself, though it's only occured on this one. Any input, or anyone else seem similar wear?