Pyrex Round Glass Food Storage Dish

I've had a similar Pyrex 4-cup storage dish for years. Love it for bringing my lunch to work and microwaving in the office. I had to buy a new one because after years of service, the blue plastic lid started to fall apart. So ordered a new one. Loaded it up, took it to work, set it in the microwave with the lid slightly on, as I always do, and first run through, the lid melted. Stuck to my lunch, melting at the points of contact with the hot food. I contacted Pyrex, and to their credit, they replaced the lid. Tried it again, same result: melted. I'm wondering if over the years, they maker has shifted to a different grade/type of plastic. In summary: it's a great product, good bowl, just don't microwave with the lid, even though the lid itself has a label that claims microwave-safe! (The one star is a result of the melting lid.)