How to fix replica set is already initialized

Ops and Admin
,
2

If i do:

cfg = rs.conf()

printjson(cfg)

cfg.members = [cfg.members[0].host="dw4-mongo-test-01:27017" , cfg.members[1].host="dw4-mongo-test-02:27017" , cfg.members[2].host="dw4-mongo-test-03:27017"]

rs.reconfig(cfg, {force : true})

I get:
MongoServerError[InvalidReplicaSetConfig]: BSON field 'ReplSetConfig.members.0' is the wrong type 'string', expected type 'object'