Hey there,

I am really sorry for the delay of this reply as it is a public holiday for us here.

It is the correct behavior, it will show this default video placeholder image if the post cover is a video by default.

Unfortunately, it is not possible to show the video thumbnail image when sharing it on the social network at this point of time.

But you can override the default video placeholder images, you can put your custom video placeholder image to your current template directory folder:

JoomlaFolder/templates/yourCurrentTemplate/html/com_easyblog/images/placeholder-video.png (use the same image name)