By 10.8 I suppose you meant CMS.Core
I would suggest you to upgrade to latest version of Commerce (10.7.3) - the message was improved so it's easier to find which value of which metafield caused the problem
After upfating to latest version the issue is resolved.
I try to create purchase order after loading the cart using cart id in one of our API.
it throw the below exception
ECApplication - EPiServer Commerce Manager Failed to create Purchase Order. Error: value is a System.Int64 but should be a System.Int32 Parameter name: value.
Also tried the same cart in the commerce manger I get the same exception.
If tried to create the purchaseorder on the same session I am not getting any issue.