How to check:
- Note the exact time and price of the stop fill from your account history.
- Open the same pair and timeframe on a different broker or data provider, adjusting for time zone.
- Compare the high/low of the candle at that time, ideally on M1 or tick data.
- Check the spread: a long position's stop is triggered by the bid, a short's by the ask.
- The other feed shows a similar price: the move was real, often a brief spike.
- The other feed shows no such price: possibly a feed spike at your broker, worth raising with support.
- The difference is the spread: the ask touched the stop while the bid chart never showed it.