I'm still learning then R5 and the only significant issue I have is that when stabilisation is enabled on the attached lens, you can't switch it off via a customised button on the body. I have configured my 1DXII and 5DIV bodies, so that holding down the DOF button disables stabilisation. For instance, this enables me to track a distant bird with the benefits of stabilisation and when that subject gets closer, or another close subject appears, I can disable the stabilisation by depressing the conveniently placed DOF button. It took a bit of getting used to but is far more seamless than switching off IS on the lens itself, particularly if its a big white lens.

Given that the R5 appears to me to be the mirrorless equivalent of the D5, not being able to configure the camera body in the same fashion is both disappointing and frustrating. Furthermore, I would also like to be able to disable the IBIS within the body for stills. I'm not aware of any technical issues that would prevent both these abilities to be implemented by firmware.