Hey alexjvcom sorry to hear about the confusion with your orders fulfilling. Shopify has a feature where you can set the system to automatically fulfill orders, and this might have caused this error.
My suggestion would be to email our support team at firstname.lastname@example.org or call Shopify at 1 (888) 746-7439. They'll be able to login immediately to confirm what occurred. Afterwards, they can send you the exact steps to make sure you can go backwards and properly fulfill the orders.
Hope that helps! Let me know how it goes and what they say.