I am running a strategy that relies on placing Stop loss market orders and I am using Postback to ascertain if the order was placed or not. Most of the times, when trigger price is below LTP for BUY orders or above LTP for SELL orders, the callback returns a failure. This experience is consistent with the documentation here: https://support.zerodha.com/category/console/portfolio/holdings/articles/kite-order-rejections. As per this blog, if validation of trigger price fails then the order may not even reach Order book. So the callback correctly displays an error message.
However few times, the callback returns a valid order_id (and no error message) and only upon invoking getOrderHistory() it is found that this order was REJECTED. Sample order IDs: 230131000103105, 230131001290015, 230131001727786, 230131003412293. This is making the Order async callback unreliable and looks like a bug.