Single sorting test case fails on different environments

[mvar]

FilterManagerBundle/Tests/Functional/Filters/Widget/Sort/SortTest.php

Line 153 in 6921be1

// Case #6: mode set to avg on integer array.

Expected order: 1 3 4 2
Usually when fails returns: 3 1 4 2
But once returned: 3 4 1 2

Test results:

Elasticsearch	Shards	Result
2.1.1	1	Runs
2.1.1	2	Fails
2.1.1	3	Runs
2.1.1	4	Fails
1.7.3	1	Runs
1.7.3	2	Runs
1.7.3	3	Fails
1.7.3	4	Fails

Maybe this is shard related issue?

Another idea, maybe on integer field calculated average value is also integer (single result does not match this pattern)?