Just like your car, aircrafts tend to encounter mechanical problems from time to time. Its just the way it goes. BA has had a few problems in the past but thanks to excellent training they have shown their true colours when it comes to pax safety.
The baggage problems are very common this time of the year and as most airlines do, they will try to have your baggage with you in a respectable amount of time. LHR, LGW, CDG, FRA and AMS are known for baggage problems but they are well used to it and deal with the aftermath quiet well.