I thought I’d share this experience in case others may be experiencing it. I use HA at 2 homes, one with a Raspberry Pi 4 and the other with a Raspberry Pi 3B+. No issues with the RPi4, but the RPi3 instance was experiencing periodic freezes. Both use Aeotec Z-Stick Gen5 without issues (the Pi4 via a USB hub).
Every 3 or 4 days, the RPi3 would just go offline and remain unreachable. It seemed to continue to function, as the Z-Wave devices continued to be controlled via automations, but the device was no longer reachable on the network, requiring me to power cycle the device to restore service. Both are hard-wired to the router and do not use the Pi’s WiFi. I use static IPs on the LAN, so this was not a DHCP-related issue.
The RPi3 shared shelf space with an Asus router - and were located very close together to the point that the devices touched. I suspected that the RF from the router may have been affecting the little PI, so I moved the RPi3 to another shelf, about a foot away.
Since that move 3 weeks ago, the RPi3 has operated flawlessly, without a single freeze or lock-out. While this isn’t a scientific assessment, the change in reliability seems to correlate to moving the Pi away from the router.
So, if anybody experiences their Pi going offline periodically, you may want to move the Pi away from the router if it is in very close proximity to it.