Duplicate results when DISTINCT querying

[MiDoWD]

Describe the bug
DISTINCT query via the 2.6.11 Java async SDK is returning duplicate results.

To Reproduce
Via the 2.6.11 Java async SDK I am querying documents with query which looks like

SELECT DISTINCT o.nest1.nest2.field as id FROM Objects o

with

    FeedOptions queryOptions = new FeedOptions();
    queryOptions.setMaxItemCount(10);
    queryOptions.setEnableCrossPartitionQuery(true);

The database has ~750 entries with 40 distinct values of this key. However after iterating all results from the pages I get, there are 69 of them, containing some duplicate ids.
When I run the same query via the Portal UI, I get the expected 40 results.
When I change the setMaxItemCount to 1000, I get the expected 40 results.

Not sure whether it's relevant, but the database uses this field o.nest1.nest2.field as partition key.

Expected behavior
DISTINCT query should not return repeated entries.

Actual behavior
Repeated entries are seen (69 entries for 40 distinct values).

Environment summary
SDK Version: 2.6.11 (first seen on 2.6.3, update did not help)
Java JDK version: 1.8.0_15 (same seen on JDK 11)
OS Version: seen both on MacOS and Linux.

Additional context