Storyline losing track of objects in story

Hi,

I am hoping that no one is experiencing this challenge but I am also hoping that someone might have some insight into what might be causing my problem.

Basically, the challenge I am running into is that I work on a project that has videos that the user watches and then they choose how to respond from some selected text options. This launches to a "response" video followed by the chance to make more choices. This all works fine when I first put it together. Then when I go into the story and make some modifications to either slides or the master slides I save the changes, preview the project, and suddenly I cannot see objects or videos that were on my slides. If the slide has a video, I can hear it start but I cannot access any buttons to make choices. When I close the preview and look at my slides, I see the video and buttons again. If I publish in this state, I do not see any buttons or objects so I cannot progress through the project. Can anyone provide any insight into what might be happening? I thought it might be memory on my system but I have a laptop that only runs Storyline and the same thing happens. If I create a new project and import the slides from this project into it I can see everything again but as soon as I make an edit the problem comes back. Looking to mine the incredible knowledge and insight this forum possesses. Help!

Thanks,

Chuck