Canon has removed the firmware v1.2.0 download for the Canon EOS R3 due to a bug in the software.
The bug is described on the DPReview Forum
The issue is that if you have v1.2 on your camera and then perform a reset the mode dial does not work correctly and you cannot change between Tv Av etc
If you have updated to firmware v1.2.0 for the Canon EOS R3, do not do any resets until v1.2.1 is released.
Canon has always fixed these sorts of firmware bugs pretty quickly, so I would expect an update very soon.
Now just like your personal computer, cameras can have software (firmware) bugs, and they also freeze up and require power disconnection (battery removal) to get them running again. As more computing functionality gets added, expect much more of this. Anyone who has ever worked in the IT industry will tell you this is a immutable aspect of computing technology.
As I always keep reminding people, there is always a cost for everything. The personal choice is if you're happy with the tradeoffs.