On a flight with Singapore airline from Zurich to Singapore with a Boeing 777 I had an aisle seat. Shortly before take off, a flight attendant approached me and told me that this seat is unsafe and I had to move seats for take off. I was given a seat that is normally used by the crew members. After take off I could go back to my first seat.

However, I felt a little bit uncomfortable after that for the rest of the flight. Who wants to sit on an unsafe seat?

So, what are the reasons that such a seat could be considered unsafe only during takeoff? What should I have done?