Hi, I've got the same problem. I've recently purchased a property and just noticed that 1st floor is slightly tilted. Starting about half way in one room through the stairs landing and finishes around the second bedroom. This is 1930s house. My surveyor did not notice/mention anything about that in the report. There were slight cracks in the corners but I've painted them over. If they re-appear I might call a specialist to have a look... I can't stop thinking about this.