10-17-2016 02:25 AM
You need to stop and take a step back. It is obvious you don't know the problem. Neither does anybody here. You are going to cause it to be worse if you proceed.
The mount is damaged what ever the cause. Take it to a pro and have them assess it.
05-07-2019 12:03 PM
I have the same issue with Canon 17-40mm F4L USM which just started showing this problem and I don't know why and how to fix it. Do you found the reason and resolve this problem?
(my camera is Canon 7D, others lens still attach normaly in it)