bookmark issue

Hello, I'm using adobe captivate version 12.4.0.20.

I have slide videos on a total of about 10 slides. I don't want to use the playbar, visually, it doesn't fit with my design, and I just don't really like it. My videos are all setup the same way. I added 4 buttons, a next button, a pause button, a play button and a back button. For that one, I just added a bookmark at the start of the slide, and I ask the button to jump to the bookmark. My problem is that on some of the slides, when I hit preview and test it, the button doesn't jump to where my bookmark is, but at some other point on the video (around 10 seconds in)... Is there a problem with bookmarks? or is it a preview issue?