Old shopping cart data not cleared by scheduled task

Hi. I have had a recent case of a client adding an item to a shopping cart back in March 2020 and then recently making a purchase where the old shopping cart item was also purchased, i.e. the "Clear content of old shopping carts" scheduled task hadn't cleaned this up. We have configured the store setting in the Ecommerce app to mark carts as abandoned after 4 hours and clear old shopping carts after 30 days.

I know that the user's shopping cart is stored in a session object so I was wondering if the only reason this has occurred is if maybe the user has kept the same session from 3 months ago? Has anyone else experienced this issue?

Thanks.