Dockerd failed to respond the rpc call from kubelet

Moby Version: 3.0.10
kubelet reported error ‘PLEG unhealthy’ and found the 1st time it happened with error “E0720 19:37:45.395520 3907 remote_runtime.go:373] Exec xxxxx ‘ls’ from runtime service failed: rpc error: code = DeadlineExceeded desc = context deadline exceeded’”
After checking the docker log, found that it looks like the dockerd got stuck after 19:32 on 20th July.

Appreciate if any idea why this happened?