So I've been trying to revamp my lens lineup and sold my Pentax 300mm f/4 prime lens on Ebay. Worked just fine before shipping it. The guy gets it, says that there's a rattling noise inside, but I can't quite understand his explanation due to his poor English. He attaches some photos but they're not very good either, still can't understand the problem. I thought he was saying there was something inside the glass rattling around. He says the lens works just fine, he just doesn't want it because of the rattling. We go to Ebay Resolution Center because I know for a fact this problem did not occur prior to shipment and he claims it was like that when it arrived. Ebay sides with him, so they reimburse him and he returns the lens to me.
So now I'm stuck with a potentially damaged lens that I may not be able to sell for the same amount anymore, and it could possibly degrade and not be useable for me either. Last thing I want to do is send it to Precision Repair and wait 3+ months for them to tell me either they can't fix it or that I have to pay several hundred more dollars to fix it. I'm pretty annoyed because the lens was freaking fine when I shipped it.
Anyway, currently I'm just trying to understand the scope of the problem, if there is one at all. I received the lens back in the mail today. Upon inspection, I can see what the problem (now) is. I'm not super familiar with the parts of lenses, so bear with me, but when you're looking into the rear mount of the lens, there's a tube just inside the mount (not inside the glass) that is grooved. It rattles around some when you move the lens, the grooved tube seems like it has become detached. That's basically it. It still attaches to the camera, it still takes pictures. Since I don't exactly know the function of this part, I can't really tell if this is a non-issue or if it's potentially an issue that's going to get worse over time and cause me (or someone else) real problems. Since many of you are much more knowledgeable than I on this subject, I thought I'd seek out your advice.
Thanks much. I'm attaching a pic to show you what part I'm referring to, it's the black grooved tube just inside the rear mount.