I have a similar issue to this topic, i use a PI4 2GB with power USB-C 5V 3A , the PI is LAN connected to router. after a few hours (or 2 days at max), the PI4 does not showing anymore in my home network and i cannot access to it, even if the LAN led is ON and nothing have been touched. to discover it again, i need to reboot the PI4 manually.
This issue happened 2 to 3 times every week.
What can i do to check this problem and solve it?