Mishap (noun)

1. An unfortunate accident or incident that happens unexpectedly and unintentionally.
2. An unforeseen event or circumstance that causes inconvenience, trouble or damage.

Origin:

From middle english meschappe, from old english meȝscieppe, equivalent to mis- + scieppe ("shape, condition"); see shape.

Examples:

1. The accident was just a minor mishap, no one was hurt.
2. The flight was delayed due to a mishap with the landing gear.
3. The party was ruined by a kitchen mishap with the cake.
4. The performance was interrupted by a mishap with the stage lighting.
5. His plans for the weekend were spoiled by a mishap with his car.