It sounds very like you have a physical problem with either your arbour, or with your chuck. My blades spin perfectly in alignment, and I cut a LOT of coils before I need to change a blade. I did once have a problem, which was entirely my own fault when I'd cleaned the system and put the arbour back on incorrectly.
I hope Dave will sort this out for you - I've always found him a very helpful guy. The only other option I can think of would be to switch to a different drill type - have you considered changing to a foredom?