Remote function call (RFC) for WS_DELIVERY_UPDATE fails w/o error message

Dear Experts,

Iu2019m using WS_DELIVERY_UPDATE to post goods issue against outgoing delivery. SE37 works fine.

RFC call from external program with the same parameters fails without returning any message.

It aborts during call and after that it becomes invalid.

Also calling BAPI_TRANSACTION_COMMIT does not help.

Any idea why SE37 works fine but RFC fails?

Anything I am missing?

Many thanks

Regards

JW