Trade closing unexpectedly

[Forex Trader]

I am a new trader and using Meta Trader for the first time. What causes a trade to close unexpectedly?

I buy 1 contract of usdchf at 2009.06.03 15:30 for 1.0686, S/L = 1.0649, T/P = 1.0731. At 2009.06.03 15:30 the trade closed at 1.0683.

I tried it again at 2009.06.03 15:33 for 1.0681, S/L = 1.0651, T/P = 1.0730. At 2009.06.03 15:36 the trade closed at 1.0675.