OrderSend - error 4059 ERR_FUNCTION_NOT_ALLOWED_IN_TESTING_MODE

In one of my EA I get the error 4059 ERR_FUNCTION_NOT_ALLOWED_IN_TESTING_MODE on a OrderSend function.

What is strange is that the first 2 orders are send correctly and then suddenly the others give all the same error 4059

Any idea why?

thanks