The detail that catches most people is that the chart doesn't show it. MetaTrader draws bid candles by default, so a short gets stopped by the ask while the candle on screen never comes near the stop.
I sketched the typical shape on EURNZD in the attached illustration. Normal spread is around 2.5 pips, then from 22:00 London the ask jumps to roughly 18 pips above the bid for about eight minutes, and a short with a 12 pip stop at 1.9137 gets filled while the bid never trades above 1.9122. Look only at the chart and you'll think someone hunted you, because the stop went 15 pips above the highest bid.

- img_13451_r1.png (101.4 KiB) Viewed 20 times
Two practical things I do. I turn on the ask line on every chart I hold into the evening, and between 21:45 and 22:15 London I don't keep any stop on a cross closer than about three times its normal spread.
The clock moves too. Rollover is 21:00 London instead of 22:00 while the US and UK are on different clocks, and this autumn that week starts on 25 October.
On the drawdown side, does anyone know a firm that spells out how it treats a spread-only breach in its rules? I've only ever seen it decided case by case.