After installing firmware 1.5, I was having my R5 freeze regularly with animal eye autofocus mapped to back button focus. I installed firmware update 1.5.1 this weekend hoping it will fix the issue. I went out today to shooting some shore birds. My R5 locked up 3 times in a period of 1.5 hours of shooting, one of the three was was with error E70. In all three cases, turning the camera off/on fixed the issue; this is different from firmware 1.5 freezes, where I had to take out the battery to fix the freeze.
Please let me know if you need more information about the camera settings. I happy to share them.