[Klaus]

https://photozone.smugmug.com/Canon-RF-100-500mm-f45-71-USM-L-IS/

[Brightcolours]

The 500mm wallaby image appears to have some severe vertical movement, creating double/smeared horizontal lines while vertical lines appear to be unaffected. Is that a form of shutter shock with the used camera (EOS R?) and the lens' IS, at 500mm and 1/200th sec? Try shooting with EFCS to see if there is a difference.
Hmm, the meerkat image (2nd one, the 1st one is a total mess) also appears to show vertical movement, at a different exposure time. As if the IS is not allowed to get to a stable situation, or there is shutter shock, or the IS is just faulty.

Not an issue other reviewers have bumped into.

[Klaus]

The tripod-based results will show it but I also thought that the IS may be the cause of the issue here.

[Klaus]

Early tripod-based testing does not suggest an optical problem.

[Klaus]

Ok, one thing.

Yours truly prefers spot AF. And spot AF is highly unreliable (and sometimes completely unusable) > 400mm.

Maybe it's mentioned in the manual but the lens came without.

[Brightcolours]

Did yours truly try that on a R6?

So now you have two issues, somehow "misbehaving" IS and spot AF not behaving like you expect it to.

[Klaus]

Lab-based images look Ok at 500mm.

Of course, I didn't try it on the R6 - besides having a life, I'm not a millionaire.
Is there any statement out there that the R is incompatible? No.
The R also worked perfectly with the 70-200 so it's not the camera.

[Brightcolours]

I just wondered if you could, to see if there is a difference with that AF issue you appear to have encountered. I'm sure the place that rents out that 10-500mm has a R6 to try it on, anyway.. If you want to find out what is going on, that is.
The lens does not determine the focus via spots or areas or points, so it must be the camera.

[davidmanze]

Did yours truly try that on a R6?

So now you have two issues, somehow "misbehaving" IS and spot AF not behaving like you expect it to.

"Your's truly" as in the above case is you BC ....... (oneself) not Klaus!

..... derived from signing off a letter .... your's truly ...... Brightcolours
. .

Your's truly 
                  Dave's cliches .......... ie. me myself I.

[Klaus]

So the manual doesn't state anything regarding incompatibilities.

A malfunctioning spot AF is not a big deal - if you know it. I reckon spot AF just doesn't work reliably with an f/7.1 aperture. On Sony cameras, the AF switches to a broader AF field, if it has issues. The EOS R sticks to the setting.

Note that the spot AF works nicely in lab conditions.

Yesterday I shot another set of 50 images mostly at 500mm. Most images were motion blurred (surfers) - which was my fault (in combination with the f/7.1 aperture) because the shutter speed was not sufficient. There was at least one shot which was sharp - albeit not usable because the composition was s**t.

One conclusion is certainly that it isn't a sports lens at f/7.1 - you just end with very high ISOs in such cases.