Front turn signal replacement problem

I am switching over my amber lenses to the clear style on my 2001 330ci. When I went to put the front turn signal lens in today, one side of the plastic "V" on the clear lens snapped as I was pushing it into place. I was very careful to make sure that the tabs were correctly going into their slots. I also used a very light, even pressure to push the lens into place. And I had no problem whatsoever getting the original amber lens back into place once the clear one broke.

I believe the plastic broke not out of my fault, but instead because the plastic was too brittle and, as it needed to flex to get into locking position, snapped because of the needed pressure on it. Does anyone know if this is a common problem? Is it possible that the lenses that I purchased are faulty (they seem to be made by a company called Depo Autolamps by the way). I want to try to get the company who sold these to me to replace them since I really don't think I did anything wrong during the installation. Any advice would be helpful...