You're only trying to take a slight curve out of the short rigid section of the wiper arm, not put a bend in it, just to clarify.
It needs to be straightened gently and a bit at a time in the vice.
If you think about it, it is the only part of the puzzzle that can have changed since the car left the factory.
The spindle hasn't moved in relation to the windscreen and the windscreen hasn't moved either.
I wasn't sure of it before I tried it, but it worked a treat.
No one can tighten the spring.
