Looking at the output of the ROC I could see the TDC in slot 18 was not initialized.
I changed the index from NTDC1+NTDC2-2 to NTDC1+NTDC2-1
it seems TDC in slot 18 is seen now.
Though when thinking about the array, we want to avoid the last TDC since it is programmed separately so the -2 seemed to make sense since NTDC1+NTDC2-1 is the last from the array but I guess I will think more about how the array is filled later.
So I think now ROC4 should see all TDCs.