Disabled text disappearing

Hi, has anyone had this problem; I'm working on a 'labyrinth' where users have to navigate through the argument of a speech by clicking on the right connecting words. If they click on the right connector, the next part of the speech comes up, with its own choices. As I don't want previous triggers to bring up past choices as users progress through the speech, I've set each text box with the correct connector to be disabled, i.e. unclickable, after it is clicked.

However, as I was going through and adding the triggers, each question I worked on caused the text from the previous correct answer to disappear completely, instead of just being unclickable. Each one worked fine until I worked on the next one. There's nothing in the states to show why this might be happening, and wondered if anyone else has come up against something similar?

Attaching the slide so you can see what I mean. (Apart from the first two, the incorrect answers are causing the screen to look a mess, but that's just due to changes I'm still to make, so please ignore that bit!)

Grateful for any help or suggestions!

Thanks