Add to cart as guest – then login – items out of stock

Love the plugin but just came across an issue. If items are added to the cart as guest, then the customer logs into their account, the items in cart then say “out of stock” because the item inventory was reduced in the guest cart and is now “out of stock” for the logged in cart. Most products on this site are unique with single quantity.

The page I need help with: [log in to see the link]