Multiple Text Entry Quiz

Hello everyone.

I am a fairly new Storyline user and I am trying to build a multiple text-entry question for which text entries have multiple possible answers...

I am using an approach similar to that described in Jeanette Brooks' tutorial, except I have "intermediate" buttons being used with variables to help deal with the multiple answers issue.

So...

I have 7 text entries (named TextEntry3 to TextEntry 9)
I have 13 hidden buttons, 3 of which (Button 3, 6 and 13) are used as the Pick Many correct answers.

Buttons 1 and 2 trigger button 3, based on the values of TextEntry3 and 4)
Buttons 4 and 5 trigger button 6, based on the values of TextEntry5 and 6)
Buttons 7 to 12 trigger button 13, based on the values of TextEntry7, 8 and 9)

The expected answers are:
TextEntry3 and 4: itu, ipf (in any order)
TextEntry5 and 6: ipvg, ipvd (in any order)
TextEntry7 to 9: ipi1, ipi2, ipi3 (in any order)
Case does not matter.

I know it's not elegant (to say the least!), but shouldn't it work?
I add my file here if anyone can offer a hint.

Thank you very much!

(PS: If I only check one of the correct answer buttons in the Pick Many answer grid, the slide behaves OK. I have problems when checking more than one. Not sure if it has to do with the sequence of triggers...)