Artefact when using animated Gif

Hello,

When I used Gif files to animate a blinking LED there is a white dot that appears  when I test my page or publish the document.

I checked the my Gifs using HTML file and they are good.

Here displayed in the editor:

Here when I run the E-Learning:

I took time to do a good job and I am very dispointed by the rendering.

Furthermore that it is the only way I found to have a blinking led corresponding to the reality without using tons of code. When I use the time line the time is not respected, blinking is too much slow. I need 200ms ON and 200ms OFF.

Have you a clue ?

Thank you !