Stuck lens?

I cross posted in KM forum, but I was wondering if third party lenses getting "stuck" on a camera is a common issue. Currently, I use only KM lenses on KM cameras. The new lens would be a Tamron.

BTW, anyone have any experience with the Tamron 100-300? The owner wants $50 for it.

I had a problem with a Tokina lens once, but it was only because one screw on the mount itself came about one turn loose so the lens was binding in the lens mount. The screw was so small that I had to use the tip of a knife to screw it back in; no problems since. I don't think that had to do with the fact that it was a 3rd party lens - any screw can work loose over time.