That's odd, I've got a couple, an SG1 and an SG2, and I can't say I've ever really had any problems with them, and I've shifted them around a fair bit. I had the SG2 on my Galaxy ages back, and then a few years ago I recycled it onto the rear of the Brompton to hold a Dinotte, much as GruB has his topeak one, and then it was on the front of the Pomp where it has moved around a bit as I've managed to break various front light mountings recently. I've never come close to breaking one, or had one come loose.
I never liked the look of the Topeak one (on websites, I've never seen one in the flesh) since I was worried that all the additional movable bits might make it more prone to breakages, or shifting about.