Reweight initial/final states cannot be found

Dear MadGraph experts,

I am wondering if it is impossible to reweight if I have proc_card as:

import model S1_LO
define p = p b b~
generate p p > b ta+ vt QED<=2
add process p p > b~ ta- vt~ QED<=2

and a single reweight card has a format of following.

======================================
change process p p > b ta+ vt QED<=2
change helicity False

launch --rwgt_name=case1
set

change process p p > b~ ta- vt~ QED<=2
change helicity False

launch --rwgt_name=case2
set

======================================

Once I do this, it fails with an error

"CRITICAL: The following initial/final state ((-4, 21), (-16, -5, 15)) can not be found in the new model/process. If you want to set the weights of such events to zero use "change allow_missing_finalstate False"
Naively, I thought by providing both of the processes, I thought initial and final state information are present but do I understand this model/process incorrectly?

Or will "change allow_missing_finalstate False" do the trick?

Thank you.