Stock not Reducing When using PayPal Standard Chckout

I have a shop/ticketing system on my website. When checking out using PayPal standard the stock does not get reduced. The order autocompletes ok, and the payment goes through (this happens on standard woocommerce shop items not just with the tickets plugin)

If I use a coupon to make the order free (bypassing payment) the stock does reduce. And when using PayPal express it does too (although for some reason PayPal express places duplicate orders – hence me choosing to use Standard)

To make sure it wasn’t a clash I deactivated all plugins other than woocommerce, and set the theme to a default one. This made no difference when ordering.

I have included my PayPal API, and then set up paypal IPN. This once again made no difference.

When looking at order notes I simply get “Order status changed from Pending Payment to Completed.” no notes regarding stock.

Im running version Version 2.6.7, running php 5.5

Thank you.