It could be you just got a bad one. Whenever I buy an aftermarket electronic sensor or switch it is typically standard motor products, and not the t series! I've had very good luck with them, and I just bought an ignition cylinder and switch for my 71 which both felt well built and work great.

There are probably other brands that are decent, but once I started using smp I've had such good luck and no failures that I've only used smp ever since (about 5 years)