The glue used on the side sticker is susceptible to the environment, making the adhesive difficult to separate from the surface in some cases if it's been exposed to extreme heat or humidity.
Here are some helpful ways to remove the sticker:
Do not use acetate (nail polish remover) on the sticker. Best practice is dish soap and warm water. For extreme cases, use Goo Gone or Micellar Water to remove the glue/paper residue.
Additionally, you could cover the residue in a soft powder (flour or baby powder for example) and let it sit for 10+ minutes, and then washing off with warm water and soap.
If these tips and tricks do not work, please contact our Customer Service team and we'd be happy to further assist you.