When these first came out years ago, I ran into several. Plastic isn't as good for product life compared to glass. Cost is a factor, but I really liked their paints. Check bottles before you leave the shop.........always.
I had a few "frozen" ones too. Looked just like the picks.
I quit painting about 10 years ago, but I was using all "water based" paints at the time, and had great results when everything was set "just right"