Enties such as thrown potions will slide and then clip into invisible bedrock border.Sadly i wasnt able to attach a screenshot but ill say how to trigger:
1. Get a creative Old-Mode world
2. Go to inisible bedrock border and make sure you touch it
3. Throw a potion in line of border by throwing it parallel to border
4. watch it silde, clip and shake

You could fix by making it die if its near the border