Fall is my busy season at work I'm lucky if I get the opportunity to shoot birds in the back yard. Be that as it may, I may be having an issue with R5 MK II.
A few days ago I went to use the camera and the battery was dead. I didn't give it much though as I hadn't used it much recently. I dropped a new battery in and charged up the dead one. The next day that battery was dead. (You're probably asking yourself if that battery was fully charged. I am too. I *think* it was.)
The camera sat for a couple days after a fully recharged battery was installed. This afternoon I set out to shoot some local birds. The battery was fully charged but a new issue arose - I had no focusing points. As a matter of fact, the camera was showing an aperture value of 00. I dropped the battery out, disconnected the lens and put everything back together. It functioned fine.
Tonight I cleaned the contacts on the camera, lens and adaptor.
Has anyone experienced something similar to either issue?
No. I have not had any issues with a half-dozen R5 IIs and I use the 500/4 IS II with 1.4x III often.
If the battery is draining it seems the camera is not turning off. I would test it with an RF lens to see if that makes a difference. Also try another adapter if you have one. Are you using a genuine Canon RF-EF?
Make sure that the camera has auto power off otherwise it will drain batteries. 00 aperture usually means that the lens is not connected, either bad/dirty contacts (wd40 is perfect for cleaning) or not fully attached. The 00 aperturebissue happened to me once, because i've touched the release button. And it wasn't locked.
It worked every single time om my SD cards contacts and on the battery contact. The old battery wasn't recognized by the camera after 7 years of usage. A quick wd40 puff on a cloth and it was all good. Do not spray directly, of course and allow time to dry. Maybe alcohol is a safer bet.
I had an unusual problem on mine. The joystick on my battery grip had gotten stuck in an "on" position and affected my focusing. Didn't realize it until I'd gotten home.