When creating a gig video, placing your gig image or thumbnail at the beginning or end of the video is best. Once you've done that, upload your gig along with the video. After 30 minutes, your video will appear on your gig. Then, click on "Gig Edit" and select "Gallery". From there, click on the "Video Edit" option. Play your video, choose your desired image or thumbnail, apply your selection, and save. This will ensure that your thumbnail is properly set.