Siebel SAI - Adding associations

Hello Siebel-Pro's,

we have made an interesting phenomen:

When trying to ad a position via SAI call to an account, we get the message:"the record you are trying to modify has already been modified".

Knowing that this is not true, investigating the log showed the following:

Before the Insert comes an Update to the account:

UPDATE  SIEBEL.S_ORG_EXT  SET MODIFICATION_NUM = MODIFICATION_NUM

   WHERE ROW_ID = :1 AND MODIFICATION_NUM = NULL;

So here we can clearly see what's wrong: Siebel searches for an account with MODIFICATION_NUM = NULL, which is of course not given here.

The SAI-Call looks like the following: