1) It really was not safe.
2) It was really not safe.
3) It was not safe really.
4) It was not really safe.
How do you understand sentences 1-4?
I see three possible meanings:
a) It was not safe at all.
b) In reality, it was not safe.
c) It was not completely safe.
I understand none of the sentences to mean (c), (1) and (3) to mean (b), (2) to mean (a), and (4) to mean (d):
(d) It was not very safe.
That is assuming normal emphasis. With special emphasis on "really was," (1) would naturally be used to affirm somebody else's assertion:
A: Tom said that riding elevators at that period in history was not safe.
B: Tom was right. It really was not safe.
Incidentally, instead of (2), most people would say: "It was really unsafe."