New to Storyline: Playhead issue

Hello. When I click Pause in the timeline, the scene goes back to the beginning. The playhead stays in the right place (170 sec, for example), but the scene displays what's at 0 sec.

In addition, when I click on the timeline to move the playhead (100 sec, for example) the scene does not display what's at 100 sec. Sometimes there is a long delay and it'll finally "catch up" and other times nothing happens at all. The scene is essentially stuck and moving the playhead has no effect.

I have a three-minute scene that's simply a recording of mouse clicks in a software program. There is no audio; I have about 12 captions.

In other words, it's impossible to put the captions in the right place because I can't pause the scene. Nor can I get to the right place in the in scene by moving the playhead.

I hope my question makes sense. I'm working on my C: drive and my PC meets all the system requirements.

I'm new to Storyline and I'm not sure what I'm doing wrong. I've seen similar posts but nothing that seems exactly like the issue I'm having. I didn't have this problem at first, which makes me think it's a memory issue. It started happening at around the tenth capture I inserted.

Any information is certainly appreciated. I'm happy to provide further details if necessary.

Regards,

Tom