In addition to @CubeAce comment, we need more information on the following:
Photo format - use MediaInfo to analyse one of the images and post the results from the Text view.
Your computer specification - see this topic for details of the information required, please quote processor and graphics card make/model in full.
Screenshots of the Program settings, Display options, and Import/Export tabs would also help
and clarification on what you mean by '4G video clips' - ie the video clips are 4K resolution or from a 4G mobile?
If from a mobile device then you are likely to have another issue with sound out of sync, due to the video being Variable framerate or the audio samplerate is incorrect. A Mediainfo analysis of one of these clips would help.