Priorities in Account Derivation Rules are not working properly

Hi,

I've configured an ADR for Fixed Assets. The ADR contains the following lines:

priority:1 -- Constant

Condition: Category Identifier XXX

priority 2 -- Constant

Condition: Category Identifier YYY

priority 3 --- Source: Asset Cost Account

Condition: Generate Code Combination Identifier IS NULL

When I execute the Create Accounting, the first 2 priorities are working fine but the accounting program doesn´t solve the priority 3 condition.

Any idea or recommendation?

thanks a lot