I have some new cracks opening up in plaster. The plaster is getting on for 20 years old and hasn't been redecorated in about 5 years. However, all these cracks are in the same area of the house - either side of an internal door and either side of an internal wall that has been knocked through. I am selling my house and the buyer's surveyor came last week. I am assuming that the surveyor will recommend a structural engineer to have a look and panicking that there may be a more serious problem. Any opinions on whether these look serious?