After returning to the lounge because Fred received an injury, there is a shot of Velma and Daphne from their backs next to Shaggy and Fred. When Velma passes Daphne, Daphne's foot pops into the foreground over the bed.
Elle only gets a couple of inches away from the right hand side of the screen and her snowboard and notepad already disappear, making it look like they've been cut in half.
When Velma says about watching all those snowboarding movies got her thinking that Avalanche Anderson must have connections in Hollywood, her left foot is hovering over the chair the latter is tied to, instead of on the ground.
When the Mystery Machine makes a perfect parking, its windows are shiny so it's impossible to see inside. The windows of the cars on either side of the van are also shiny as well.
In the end, no film crews or audience are visible at the supposedly high-profile competition.