Stopped Working - Scared our house guest to death!

I rate it three stars for installation, four for room darkening, and negative five for durability. That averages out to 0.667, but one is the lowest possible rating so I rounded up. It went up with some difficulty, and wobbled pretty bad during operation. It worked fine for maybe the first six uses, but then OMG! Ours is the largest size, so it packs a mighty wallop when out of the blue it decides to roll itself up in three nanoseconds, flinging itself right out of its brackets in the process, and scaring the daylights out of our sleeping guest. The next day, I readjusted it (a tedious process for a fully released shade) and it held for several minutes. This time, it actually damaged our window box as it imploded and flew out of the window frame, scaring the bejeezus out of me in the process. DO NOT BUY THIS PIECE OF JUNK! No, serious, don't buy it. The decision to do so will haunt you for the rest of your days.