Ghost trigger appears when I import a Stoyline project

Hi!

I am importing a storyline project in another Storyline project (File>import>Storyline).

After importing the project, any frames which contained questions show "ghost triggers", that is, triggers that were not there before.

These ghost trigers consist in: "Go to next frame when the timeline of this frame starts" in each "question" frames.

The triggers don't appear in the triggers list (right side of the screen), they just appears as a red arrow in the list of frames on the left side of the screen, as an indication that there is a link to next frame. When I click twice over the red arrow, a dialog box appears, where I am (supposedly) able to edit the trigger characteristics, but the characteristics are not really editable.

I can delete the red arrows by clicking the right button and selecting "disconnect link" 

Has anyone experienced this problem/behavior?  is there any solution ?

I would expet an import to leave the imported frames intact... but it appears that Storyline adds triggers on its own.