Screen Flickering on Playback

I have recorded a Software Simulation. I now want to add audio. In the past I have merged the slides and then recorded the audio.
Having merged the slides, when I try to view the screen as I record audio, I get a constant black flickering on my viewing screen. Is there a setting I have got wrong?

Hi,

Can you please share the project and its external data folder named in the pattern PROJECT_FILE_files if any so we can check? If these files are large, please upload them to a cloud storage site like Google Drive then email the link to us at support@atomisystems.com

Regards,