First of all I have very limited knowledge of magento so please excuse my stupidity if this is easily resolvable or I'm not explaining things properly.
The only payment option I use is paypal express checkout and I offer 2 shipping methods - a flat rate of £2.99 for orders under £25 and free delivery for orders of £25 or more.
Since Monday any customer placing an order of £25+ and selecting the free shipping option is experiencing problems. They are completing the payment process with paypal however the transaction is failing and they are then being redirected back to my site with an error message "please specify shipping method". Alongside this message is a drop down box to select a shipping method, however it only provides customers with the option of £2.99 shipping, not the free delivery they initially selected and qualify for.
I've never had this issue before and customers placing orders of less than £25 and selecting the paid for delivery option are not having any issues.
Any advice on what might be causing this and how to fix it would be greatly appreciated.