Before this time, many time-consuming operations happened at the primary node

Secondary log:
2018-07-26T04:01:00.023+0000 I REPL [ReplicationExecutor] Error in heartbeat request to 10.0.189.100:27017; ExceededTimeLimit: Operation timed out
2018-07-26T04:01:04.254+0000 I REPL [ReplicationExecutor] stepping down from primary, because a new term has begun: 98
2018-07-26T04:01:04.322+0000 I REPL [replExecDBWorker-1] transition to SECONDARY
2018-07-26T04:01:05.413+0000 I REPL [ReplicationExecutor] Member 10.0.189.100:27017 is now in state PRIMARY

I have archived (tar or zip) the $dbpath/diagnostic.data directory from each node.