I get an error "required field not found" .

I get an error "required field not found" .

"code":"MANDATORY_NOT_FOUND","details":{"api_name":"Last_Name"},"message":"required field not found" 

I am getting such an error. The error also states that the Last Name field is empty, but I'm not sending an empty value. This is how I send it.I don't get this error on every transaction.

{"data":[{"Last_Name":"KÖMCÜ", "First_Name": "Oğuzhan", "Phone": "534*****47", "Email":"oguz1234@gmail.com"}]}

This is an example json file.