Problem with presents

I am new to Libre. When I prepare a slide presentation, I put a color as background for slides. When I advance the slides, with or without text, I get white dots and streaks that run from the top right hand corner of a slide to the bottom left corner. When I go in reverse, the white does and streaks are absent. What’s going on? I obviously can’t run a presentation in reverse order, so the program is useless to me unless I can fix this. I know it’s not my computer since I tried it on an 11.6 laptop, and on a 15 inch laptop, and Kingsoft WPS runs just fine.