Custom fields in checkout page with checkout extension

[Ponmari]

I am trying to create custom fields in checkout page with checkout extensions, i want to include all the form fields like textfield, textarea, phonenumber field , select, radio checkbox. but when i tried to submit the form by clicking pay now button, i get an error like  "There was an issue creating your order. Try again, or contact us for more details."

And Console shows 

"Metafield - index 0 - is not the correct format., Metafield - index 2 - is not the correct format."

I created custom metafields with namespace and keys in orders  metafields in custom data section.

Can anyone give solution ???