Hi,
I had one Raspberry PI 4, but returned it on warranty. It was "freezing" for some time on regular basis, once every few days and required reboot. Finally, it stopped to read microSD cards, green LED blinked 4 times.
I received replacement, it worked fine for few days, but same problem started to occur, freezes that required reboot and now it won't boot, there's solid light from red and green LED. Tried to re-flash image to microSD card, tried another card, tried recovery.bin, but RPI won't read it.
I use original RPI 4, 5.1V/3A power supply, it is connected to ethernet, external HDD with USB3 and there's fan, NOCTUA NF-A4X20 5V/100mA connected to 4 and 6 pin on GPIO. I measured voltage between some test points on board and it shows 5.25V, so within correct range.
Temperatures were ok (~40-50°C), Raspberry was on 24h, Kubernetes on Raspbian was running on it with some small, constant load.
Bad luck and I should ask for another replacement or do I do something wrong that leads to this failures?

