if habe an issue as follows:
For use with my vintage manual lenses I normally use adapters with dandelion or EMF AF-confirm chips. Some EOS-bodies have in the 22:00 clock-position a mechanical switch to indicate the presence of a lens. If this switch is engaged, the camera expects to find an electronic contact via the bayonett-connection, otherwise it reacts with an ERR-Message and stops working. I know this issue with EOS 1Ds and EOS D60. A small piece of paper applied to the switch solves the problem, the body works perfectly with the adapters and focus-indicators work. Until you mount an EF-Lens to the bodies, then the paper often falls out of the switch and if you do not recognize it, the next change of the lens to an adapted one lets you miss the af-signalling or receive an error from D60.
My solution: fix the switch with a small amount of cyaneacylate-glue, which is easy to remove with solvent in case this becomes nevessary. Works perfect with adapted lenses - but if you mount an EF-Lens, the glued switch is forced down mechanically, or the EF-Lens is not mountable due to a mechanical stop.
-> inspection with my eyes did not teach me what the problem is, moving the small switch did not show me some other moving parts in the bayonett. So what causes the mechanical stop in mounting an EF lens with the switch fixed in the upper position? Anyone here to be able to give me some advice how to handle the problem?