Strange behaviour in HU Packing with BAPI calls

Hi,

I am using the following function calls to perform packing on a delivery document via an interface.

1) BAPI_HU_CREATE

2) BAPI_HU_PACK

3) WS_DELIVERY_UPDATE

For a single delivery line and single HU it works fine all the time. When I start getting more complicated with 2/3 delivery lines and 2/3 HU's I get a strange effect. If I run it through debug quite slowly it works. But leave it to run itself and the BAPI_HU_PACK runs twice in a loop it seems to fail second time around by not passing back the HUITEM results correctly - it does however return a sucess code.

Am I missing something really obvious about stringing these FM's together in an ABAP program?

Julian