Split Cluster Map data test (random fail)

The Test
4 Node cluster with backUpCount = 2 
1 map is created put 1000 items 

4 Node cluster is Split in half, giving 2 x (2 Node cluster) 
clusterA(node 1, node 2) and clusterB(node 3, node 4)

assert the size of the map from A and B == 1000

The result,
This test fails in a small % of runs?

The map from A and B is not 1000

some times the map size from 
cluster A(node1) and cluster A(node2) is not equal
or
cluster B(node3) and cluster B(node4) is not equal

Note
I can send a pull request to a personal repo for independent review / test runs ?