Incorrect Layer on modified Multiple Answer quiz slide not appearing

Hi, I have modified a Multiple Answer quiz slide by importing the basic one, restyle it slightly and eliminating the Try Again layer.

It now has the original Correct layer (working fine) and a modified Incorrect layer, where I simply added two extra button to the existing one (copy/pasting the original one and typing over the tag, renaming them in the timeline, readdressing the jumps).

The Incorrect layer, now shows a button leading to the previous slide (containing a video, that learners can watch again before to re-attempt the test), one that leads to the same quiz slide (Jump to this slide when user click 'Try Again') and one that Continues (Jump to the next slide). 

There is NO RESULT SLIDE. The sequence in this scene is:

1-Slide with Video and animation (n)

2-Quiz (n)

3-Slide with Video and animation (n+1)

4-Quiz (n+1)

Nothing special. We have decided (long story) to give:

-Feedback by question

-Shuffle to None

-Score by question (but not counted anywhere)

-Attempts to Unlimited

There are 4 answers. A and B are correct. B and C incorrect. These are correctly ticked (A+B) in the Form View. Rest is unticked. 

Both Layers (Correct/Incorrect) have object triggers for each button, with:

a) 'Hide layer this layer when the user clicks on (button name)'. I checked and rechecked that all button tags on the timeline are correct and unique.

b) Jump to (pertinent slide) when the user clicks (pertinent Button name - each button it's own destination)

Both Layer has Visibility - Hide other slide layers and Automatically decide Seeking (not really into play here) and ALL base layer options (1-prevent & 2-pause) ticked, with Revisits set to Reset to initial state.

THE PROBLEM IS that whilst checking the corrected answer see the Correct layer working fine, for the Incorrect layer choosing the incorrect answers (one or both, or both with only one correct plus two wrong) does not make the Incorrect layer to appear, when clicking Submit. So it seems that the problem is in the way Submit is set. 

On the Base layer, the Submit button (modern player) has a trigger that says Submit Multiple Response when user click submit. I have changed the name of the quiz slide to KC DIQ 1 but this should not be the problem, cause the Correct layer works. It's the incorrect layer that does not show up and I cannot understand why, cause everything seems in order. Also, the slide properties (base layer) are Slide advance by user, revisiting reset to initial state, result slide none, navigation Prev Next and Submit. Player features default.

I cannot share the file unfortunately as it is confidential. Anyone can see what I may be doing wrong, cause I am stuck.

Thanks for the help.