Может еще в метод findPrintoutJournalNum_CustInvM15_RU таблицы NumberSequenceGroupRef передавать false ?
X++:
public static NumberSequenceGroupRef findPrintoutJournalNum_CustInvM15_RU(NumberSequenceGroupId _numberSequenceGroupId,
boolean _update = false /*true*/)
{
return NumberSequenceGroupRef::find(typeId2ExtendedTypeId(typeid(PrintoutJournalNum_CustInvM15_RU)),
_numberSequenceGroupId,
_update);
}