Progression Button Issue - Buttons Not Appearing When They Should

Hello! :)

I have been looking through similar discussions threads and have seen that others have the same issue as me but their fixes haven't worked unfortunately.

One of our courses has been live for sometime and over the last few weeks a small amount of people (not everyone) can't get past the same point due to the next button not appearing. This works for majority of people including myself. We have had to remove playback bars from our videos as we need the user to watch the content before moving on.

We have tried a few things:

1. Have next button set to 'hidden' until the media finishes then state changes to normal
2. Have next button set to 'disabled' until the media finishes then state changes to normal
3. Have next button appear at a certain point in the timeline (timed to length of video)

Yesterday, I took the video files out of the course and embedded them from Vimeo and upon testing I have been able to replicate the problem. Now no matter what I do I can't get the next button to work.

I read threads from around 5/6 years ago and apparently there is a known bug in Storyline causing this? It just seems very bizarre that it was working and now suddenly doesn't.

Any help would be appreciated, thank you.
Deane