Same here, and to be honest, I am not a fan of the brown ones as I find they take longer to clamp and unclamp.I had that problem with the last batch I bought, along with the problem of being unable to close/loosen some on mugs with the smaller handles. I got around this simply by bending the small square locking tab on the large side of the clamp with some pliers. They all work fine now.
Its all horses for courses I suppose