Had that problem with my 360J just the other day. I had noticed it feeling like the cylinder might have been hanging up a bit and while fiddling with it, opening and closing it several times, the problem got progressively worse until it got stuck and felt like it was going to stay that way. I got it open one last time and found that the ejector rod had unscrewed to the point that it was hanging up. Luckily I hadn't bent it. I screwed it back in tight and now it's fine. Of course it took me a minute to figure out that the threads were reversed!