Hi chacjo99 ,
I can see 2 propable issues here, one there is some kind of error in the db or second there is another plugin invloved.
You can test the second by deactivating all plugins in your store and leave only 2 of them, WooCommerce and the free ATUM plugin.
Check if it works. If it does then the issue is another plugin. You can start activating one by one and see when it happens.
Pavel