Linking buttons to a video

Hi all,

Wondering if anyone can help me get around a problem I'm having with regard to interactive buttons appearing during a video.

At the moment the video plays at the start of the slide so the timeline of the video and the timeline of the slide are the same. I have a series of buttons I am trying to link to appear at certain times in the video, which worked fine as I could pause the video and the slide timeline in the same click and keep them aligned.

I have added playback controls to the video to show a video progress bar. I have managed to stop the user being able to pause the video using the playback controls by putting transparent boxes over the top of them (because this causes the 2 timelines to lose sync), meaning to play and pause the video they must use  the custom buttons I made which pause and play both the video and the slide timeline which keeps them both in sync.

My problem comes in that I want the user to be able to use the seek bar to scrub back and forward though the video, however, doing this puts the timelines out of sync and so the buttons then do not appear when they are meant to.

Does anyone have a solution to this other than to not allow students to scrub back and forth?

One possible idea I had was that I might be able to link the appearance of the buttons to the timeline of the video, rather than that of the slide, but as such, I haven't been able to do that?

Any help you can offer would be greatly appreciated as this is quite a time pressured project! Thanks very much!