HPCC-11400 Fix issues with balanced splitters

Signed-off-by: Gavin Halliday <gavin.halliday@lexisnexis.com>
Merge pull request #6289 from ghalliday/issue11400

HPCC-11400 Fix issues with balanced splitters

Reviewed-By: Jake Smith <jake.smith@lexisnexis.com>
Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>