On a general note, you should always mention thie Country code for a Payroll problem since some Payroll elements are Country specific.
On the subject of the problem you face, as mentioned by Jörg, you should check the value of Processing Class 10 for all IT0008 WageTypes.
Next, if you execute a Simulation for one employee with the "Display log" box checked, drill down into the log to look at Function PARTT, then at Function GEN/8 and the PCRs that follow it.