"We purchased ours on a trip to Walt Disney World. I wasn't so sure about them, but we have had no issues... Some tips for other users...
Make sure the Lego bumps are NOT in the mold and that the sticks are completely snapped into place.
Fill to top and seal the mold. If you tip, not to worry, they seem to fill back up once level again.
Our kids have totally enjoyed them and we use them as fast as they are made.
Price is a bit high and I had to think twice prior to purchase, but the kids pooled their money together for half the cost, so it obviously meant a lot to them.