I've shot ~4600 shots thus far with my R5 since receiving it in early October, and love it so far. With that said, unfortunately the freezing/lock-up issue absolutely is a thing. In my experience it has only ever happened while combined with the EF 500 MkII + using the electronic shutter + shooting continuously. I have not seen it in the other lens combo I've used it with (EF 100-400 II, RF 24-105 f/4), but I also have not tested those lenses with electronic shutter/fast continuous shooting.
It has happened to me three or four times now, and caused me to miss shots each time (usually in the middle of a burst while tracking birds in flight shots). Each time it hanged for 10-20 seconds or so (turning off the camera does not do anything), and then rebooted by itself.