I remember reading about an accident where a big, expensive communications satellite actually fell off it's mount and landed on the floor of the room where it was undergoing final assembly and preparation (I believe). It was supported on a tilting mount, and it was raised up without the mounting bolts having being in place.
The time frame is roughly two years ago (~2013 to 2015).
Recently I searched for the news again, and I can't find a trace of it on the internet!
Payloads are built to endure serious vibration and shock in order to reliably survive launch with a wide safety margin. However, when a rigid object without "crush zones" or shock absorbers falls and lands on a hard surface, accelerations can be 100's or 1000's of gees for milliseconds.
Any idea which satellite it was? A link would be great.
The idea is that even in the 21st century, rigid adherence to detailed written procedures as well as writing those detailed procedures are still both really important!