I mainly shot .38Spec through my own 686 for years and never had this problem but it did get cleaned (especially the front end of the cylinder) after every time I shot it with .38's.
The 629 was also doing this though...
Could it just be that they haven't been thoroughly cleaned correctly?
The rounds dropped in OK but I've never had cases that hard to remove before.
At our club you can only ever put Factory loads through club guns, reloads are a big no 'cause you never know just what is in a home load.
Could the cylinder bores be excessively worn as I have no idea just how old these guns are? I know the Python has been owned by the same guy for 25years+ and has put 1000's of rounds through it in its lifetime.