"failed to send out heartbeat on time" when using static mode

[typhoonzero]

logs:

Jun 12 03:04:01 hlg-wuyi-coreos-01 etcd2[4187]: server is likely overloaded
Jun 12 03:04:01 hlg-wuyi-coreos-01 etcd2[4187]: failed to send out heartbeat on time (deadline exceeded for 86.557859ms)
Jun 12 03:04:01 hlg-wuyi-coreos-01 etcd2[4187]: server is likely overloaded
Jun 12 03:04:32 hlg-wuyi-coreos-01 etcd2[4187]: failed to send out heartbeat on time (deadline exceeded for 10.632199ms)
Jun 12 03:04:32 hlg-wuyi-coreos-01 etcd2[4187]: server is likely overloaded
Jun 12 03:04:32 hlg-wuyi-coreos-01 etcd2[4187]: failed to send out heartbeat on time (deadline exceeded for 10.801399ms)
Jun 12 03:04:32 hlg-wuyi-coreos-01 etcd2[4187]: server is likely overloaded

etcdctl works fine:

# etcdctl member list
251125c4d7f71035: name=hlg-wuyi-coreos-03 peerURLs=http://172.24.3.221:2380 clientURLs=http://172.24.3.221:2379 isLeader=false
8daf20902656d961: name=hlg-wuyi-coreos-02 peerURLs=http://172.24.3.220:2380 clientURLs=http://172.24.3.220:2379 isLeader=false
e06797cebe158b25: name=hlg-wuyi-coreos-01 peerURLs=http://172.24.3.150:2380 clientURLs=http://172.24.3.150:2379 isLeader=true
# etcdctl ls
/coreos.com