Thanks for your answer; in fact i was thinking about "how to check that an order has been really filed ? "
I cant speak about the recent fxcm servers management (and their common errors), maybe now everything is transparent. But quite all brokers claim they dont requote, even if quite every day, some orders are refused due to "server busy" or "requote" (at least the broker i'm using is still weirdly acting, even its one of the "we never requote" claimer).

As Zorro will be also able to file orders with the other MT4 brokers, that question is not deprecated (sadly).