problem with gaz coilovers

[newdude]

Gday Guys and girls,
Gotta little prob im hoping someone can help me with, the rears have been bottoming out, banging and crashing over the slightest of bumps, i raised it 2cm and it was even worse, when i measured the height again it was only half a cm higher than before raising them. The fronts were easy to raise but when i tryed the rears they didnt want to turn and the springs kept catching and making it harder to raise.
Any ideas on whats going on?
Cheers