In the USA, they would probably say Murphy's law. Just another way of saying like bad luck that always happens. For example, great it's been dry all summer and on our wedding day, it decides to pour with rain as sod's law,. Next is the phrase a spanner in the works - this is an event that disrupts the natural pre-planned order of events. So you've got here are the way that things have been planned, here is how we expect everything to happen. But if you throw a Spanner in the Works, it means you ruin or everyone's plans and complicate the situation.