adding a 1.7.1 node into mixed 1.7.0/1.7.1 cluster causes data loss on active items and leaves the cluster in an imbalanced state

1- setup cluster of 3 nodes ( 1.7.0)
2- put 420k items or more
3- add a 1.7.1 node , rebalance in. everything looks good
4- remove a 1.7.0 node and rebalance out, still looking good
5- add some items
6- remove another 1.7.0 node and rebalance out , still looking good.
7- add some items
8- rebalance out another 1.7.0 node , we lose 10% or more active items