Rebalance add node with backup service failed in AWS

Install Couchbase server 7.0.0-5219 on 4 amazon linux 2 in EC2.

Initialize a node with services: kv,index,n1ql,fts,backup

No bucket create yet.  Add 3 nodes with service at each node: kv

Rebalance.  Rebalance failed almost instantly.  Try rebalance again, still fail with errors

Rebalance exited with reason {{badmatch,failed},

[{ns_rebalancer,rebalance_body,5,

[{file,"src/ns_rebalancer.erl"},

{line,543}]},

{async,'-async_init/4-fun-1-',3,

[{file,"src/async.erl"},{line,191}]}]}.

Rebalance Operation Id = 1088e9b062532acf6b3eb792538e4981