Hi,
You can't push any null values to Financials API, we strongly recommend not sending fields you do not need.
For the employees that give an error, make sure that the financial details under the employee is set to the values that you want, and that all mandatory fields are set.
If these are set and you are still having issues, it could be due to an account being used on the employee that has been modified/disabled since it was initially set on the employee:
... View more