IDoc Adapter doesn't work with LS

Hi,

we send IDocs through the XI System:

R/3 IDoc -> XI -> R/3 IDoc

First we set up a SEQJET02 IDoc with partner type LI and it works fine. Then we started with MATMAS05 and partner type LS and we get an uncaught exception at the inbound queue (SMQ2). The same channels are used on both scenarios.

The IDoc shows an error in queue in SXI_MONITOR.

I opened the same MATMAS IDoc in WE19 in the sender system and changed the header data from LS to LI and used a customer number as partner and the IDoc get through XI (of course it causes an error in the receiving system but it passed XI!)

Does anyone have an idea?

Regards

J.