Thanks guys - appreciate the input. I've got a set of 4 blades coming that are 4TPI 1/2" ones, so deeper than the 8mm one that was on it until a few hours ago.
I'm really curious about this though and I hope someone will help me understand, it seems common people suggesting that it's often a 'bad' blade that can cause this, and I accept that from the number of people who say that, but what is it about a blade itself that would cause it to either work well in respect of twisting like this one was doing, or running nice and straight? I realise you get good & bad quality products of course, but what physical thing is it about a blade that would mean it goes off on one like this instead of running true?
I know most people will be happy enough with "Don't honestly know, but they just sometimes do", but if someone know's I'm just interested to understand why.
Cheers :)