clamd randomly stops

I am using clamav in conjuction with c-icap to filter content with squid. I am also using the safebrowsing functionality of clamav to block access to bad domains. For some reason or another, clamav (clamd), suddenly stops running and I see that the c-icap service cannot connect to socket clamd socket. However, I don’t see anything in the log files indicating why clamav suddenly stopped.

I checked the following basics:
1. clamav logs (syslog output)
2. free space
3. dmesg

[Unit]
Description = clamd scanner (%i) daemon
After = syslog.target nss-lookup.target network.target

[Service]
Type = simple
ExecStart = /usr/sbin/clamd -c /etc/clamd.d/%i.conf --nofork=yes
#Restart = on-failure
Restart = always
PrivateTmp = true
PIDFile=/var/run/clamav/%i.pid

[Install]
[email protected]
WantedBy=multi-user.target

Any ideas what may be causing clamav to suddenly stop?