502-FunctionInvokeExecutionError

When i try to invoke oci document generator function,at the first try it shows error message, 2 time it is working
Invoking a function returns a FunctionInvokeExecutionError message and a 502 error
{"code":"FunctionInvokeExecutionError","message":"error receiving function response"}
Fn: Error invoking function. status: 502 message: error receiving function response

Any solution for the issue?