The lights themselves are very nice.

It's just the battery packs which are unreliable. The batteries probably are of good quality too. However, the 4 pack is connected via narrow thin metal strips, and the two wires out to the light itself are connected to these metal strips with a tiny amount of solder.

On my battery pack, the solder broke on one of the wires. I simply taped the soldered wire back in place and the light works once again. Hardly a long term fix but it works for now.

I don't know what the actual magicshine battery packs look like, but there is likely an upgrade in construction?