my cluster is 4.4.8 with three shards.
cluster upgrade from 4.4.4 to 4.4.8. cluster is ok.after one hours,there is secondary crash ,indicates _id duplicate key .
{"t":

{"$date":"2021-08-17T18:54:43.182+08:00"}

,"s":"F", "c":"REPL", "id":21238, "ctx":"ReplWriterWorker-0","msg":"Writer worker caught exception","attr":{"error":"DuplicateKey{ keyPattern:

{ _id: 1 }

, keyValue:

{ _id: \"0be47ed91b91474f8a96429fa7d3cfec\" }

}: E11000 duplicate key error collection: customerService.TrackerDetail index: id dup key:

{ _id: \"0be47ed91b91474f8a96429fa7d3cfec\" }

"