EOS R5 Mark II + RF 600mm F4 L IS USM switching to manual focus

[Smews]

I have started having issues using my Canon R5 Mark ii with the RF 600mm F4 L IS USM lens. Occasionally, it switches to manual focus mode, by itself. I.E. I do not change the lens switch or any other setting, but auto-focus stops working and the viewfinder shows manual focusing aids. Turning the camera off and on does not fix it. However, turning the focus ring does! (I don't remember changing any settings that might cause this and I do not remember it happening before the last week.) Any ideas what could be the problem, before I send them to Canon to be fixed, only to be told it is a user error?

[Waddizzle]

“ I will check the contacts for anything obvious, but I have switched in/out my RF 1.4x TC a few times, so my guess is that should have resolved a contact issue. “

A teleconverter?  That’s new. 

Does the issue appear with or without the TC installed?  Let’s test and use the lens without it.  Maybe you have a faulty TC. 

[Smews]

Sorry I did not mention it originally, but it happens both with and without the TC, so did not think it important. Of course it would probably be cheaper to fix if it was the TC 😀

I will be doing some testing to see if there is any pattern, etc.

[Smews · Accepted solution]

I thought I would follow-up in case anyone else has the same problem.

I found time to send the complete setup to my Canon Service Centre and it is now fixed. Actually, there was nothing wrong with it 😀. The other thing I neglected to mention was that the lens has a Lens Coat camo-cover on it. It appears that the covers over the focus ring and the focus preset ring had moved, such that moving the focus ring also moved the preset ring and held it in position. Apparently doing that switched to manual focus mode and caused the problems I had been seeing. (Hence turning the focus ring the opposite direction freed up the preset ring, enabling auto-focus again.)

Simple fixes are rearranging the ring covers or turning the preset function off. 

All a bit embarrassing, but glad it was nothing serious wrong.