I bought a well-used 5D Classic. serial# 2308028xx, with unknown number of clicks. Camera works fine, and the mirror seem to have the reinforcement service done. Only problem is with 1/6,400 or 1/8,000 shutter speed. I searched about it here and on dpreview.com forums, but the answers are inconclusive. Many say it's a sign the shutter is approaching its end of life, others say it may not be. I think it's best to just show you - dark band along the top, but not totally horizontal; metering gets screwed up and ended up underexposing. Both shot with 35/1.4L on a fairly bright day. Has anyone seen the same and know exactly the problem?
1/8,000, f3.2, ISO 200:
1/8,000, f1.8, ISO 100: