In window Matching-PO-Invoice-Receipt I always get IndexOutOfBoundsException when trying to match one line of purchase order to many lines of material receipt. For example you can create purchase order with one line and material receipt with same product but more lines. Then complete both of these documents and then go to Matching window. After selecting PO line, related MR lines and click Process, i always get the Index Out Of Bounds Exception (this happens when bottom table is reloading). But it looks like the bug is in ZK framework. This happnes only when you want to match one line to multiple lines. If the matching consits of one PO line and one MR line everything is fine.

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https://groups.google.com/forum/#!msg/idempiere/KnTXcUpJ21Y/PfUAIoWZR7YJ