In GT++ 1.6.99, it works flawlessly.

As of GT++ 1.6.110, this no longer works unless you have a Soft Mallet to trigger individual washes, but it does correctly process 2 items.

Issue is ongoing currently and can be reverted by going back to GT++ 1.6.99.

GregTech 05.09.32pre1
IC2 2.2.827-experimental
GT++ Single Player
Issue Class: Major

Please report the issue properly.
https://github.com/draknyte1/GTplusplus/wiki/Github-Issue-Format

Feel free to edit this one and comment, so it can be reopened.