Stop-limit orders on MT5 do something other than expected

[Amanhasnoname]

A stop-limit order is a two-stage instrument. First a stop price is reached, which activates a limit order at a second price. The limit order then sits in the book and waits to be filled at that price or better.

Scalpers sometimes adopt it to avoid slippage on breakout entries. The idea is sound: trigger at the breakout level, but refuse to pay more than a set price. The catch is that fast breakouts often blow through the limit price immediately, leaving the order resting unfilled while price runs away.

That means the protection against slippage becomes protection against participation. The trade that was avoided is often the best one.

A related surprise is that after the stop triggers, the limit order becomes an ordinary pending order and can be modified or deleted like any other. Some traders forget that and leave a stale limit behind after conditions change.

Test the behavior on a demo during active hours to see how often the limit fills versus gets left behind.

What fraction of triggered stop-limit orders actually fill in live conditions?