First off, I'm new here, so my apologies if this isn't posted in the right place. I purchased a used Canon 500mm f/4 lens a few weeks ago. The date code shows it to be manufactured in 2003, but it's in immaculate cosmetic condition: no paint chips, glass elements are spotless, etc. I used the lens for about 200 shots with no problems. However, just yesterday, the image stabilization has become "jumpy" in the vertical direction (when the camera is in landscape orientation). The jumpiness stays in the same direction relative to the lens even if the camera is in portrait orientation. This tells me that something is wrong with that axis of stabilization. By "jumpy," I mean that the image will float up or down quickly and jitter itself up or down, all randomly. It moves far too much to attain a clear photo at reasonable shutter speeds for this lens. My question for y'all is this: is there anything I can try that might resolve this issue before I send it to Canon for a costly repair? The lens's electrical contacts were clean, but I cleaned them again with alcohol. I tried the lens with and without an extender. I tried it on a 7DII body and a 5DIII body. I tried it with and without a tripod. No matter what I do, it still has the jumpy behavior. It's mighty suspicious that this behavior started shortly after Canadian border patrol searched my car, but I figured these lenses are too tough for that to matter; after all, I see these lenses banged up all the time, and they still work fine. I think I'm destined to just use the lens with IS turned off until I'm done traveling in a few months, but hopefully (though I fear unlikely) someone has a simple fix. Thanks!