Very odd situation where course doesn't work without an "empty" trigger

So first up, unfortunately I can't share my .story file as the content contains proprietary information. But all the same I am interested to hear if other users have encountered a situation like this.

2 years ago I built a very complex story, with branching, lots of variables etc etc. As part of this I had  several slides with "Pick Many" interactions with a custom Submit button, a rectangle shape which I named "Submit BIg 1" (typo unintentional!) It took me a while to get this Pick Many interaction working the way I wanted, so once I got it working as I wanted on one slide, I duplicated this slide to create my other Pick Many questions.

Now it's 2 years later and I've opened this .story file for the first time in a long time. On my "pick many" slides, I notice there are 2 redundant triggers attached to my Submit ("Submit BIg 1") button. Oddly, I can't delete these. Odder still, if I disable both of these triggers, my interaction stops working! In that, if I press Submit, it will not submit the interaction or show me any feedback layers. But I leave either of the empty triggers enabled, or leave both of them enabled, it does work.

Has anyone else encountered this odd behavior? I truly have no memory of these triggers from when I built the course, but I suppose they must have been there.....as it is for now, I am not going to rebuild or risk breaking my course, I just don't have the time, so I will leave these empty triggers where they are and enabled (not that it will let me delete them even if I wanted to!). But I'd love to understand how this might have come about.