Put the summary of the bug you're having here

What I expected to happen was that the rails would face upwards, diagonal to the blocks.
What actually happened was that the rails faced opposite to the blocks.

Diagram:

what i thought would happen:
/b
/bp

what happened
\b
\bp

b=block
p=power source
\=backwards rail
/=frontwards rail

Steps to Reproduce:
1. face north or south (east and west do not trigger the bug) by using f3
2. place down 2 blocks diagonal, like
b
b
3. put down two rails.
/b
/b
4. power the rails and the two rails should flip:
\b
\bp