my guess is that 'wan' isn't an actual interface as far as the ping command goes.
To test you need to use
ping -I wan -c 3 1.1.1.1
expect it to fail as 'wan' isn't the underlying interface name. From within luci go Network->interfaces and look under the 'wan' interface icon and use the actual interface name, something like 'eth0' or similar in the watchcat config
Watchcat uses the configured interface name in the ping command (see above)
[edit] luci-app-watchcat has a dropdown list of the actual interface names to ensure correct naming
Wed Jul 27 20:51:06 2022 daemon.info watchcat[14595]: Could not reach 1.1.1.1 via "eth0" for "3420" seconds. Restarting "eth0" after reaching "3600" seconds"
"ping -I eth0" works. Before that I tried 8.8.8.8 and the problem was the same. I have internet but rebooting router/interface is pointless if connection is fine.
My openwrt version is "SNAPSHOT, r20156-0f301b0b1d" with watchcat - 1-16.
On other openwrt (the same hardware) router I have watchcat - 1-14 and there are no issues at all.