Utilize your financial knowledge, give your answer or opinion to the input question or subject . Answer format is not limited.

Setting a trailing stop loss at $39.70 bid price, stock sold at $41
Is this due to the delay?  Yes, but the delay is caused by your broker and its affiliates.  Trailing Stop Order is not exchange native, meaning that the broker is responsible for keeping track of whether the stop price has been reached, and the broker is responsible for sending the subsequent Market Order to the exchange.  For certain exchange, even Stop Order or Stop Limit Order is not exchange native.  Is it common to be so different? No, only in times of extreme volatility.