Had a problem with my poi today, didn't see anything here on it, but I figured out how to fix it so thought I'd share.
Have the rainbow LED poi I got here on HoP. Today one of them seemed to be missing a color. Would cycle through a few colors, go dark, come back in to the cycle. What I found was inside the battery tube there is a ground on both sides. I guess after bouncing off the walls, ceiling, and occasionally my head

the tube had shifted or warped a bit and one side wasn't making good contact.
Pulled out the batteries, and the tube with the chip and LED attached to the end can be slid out. It's a little tight but it can be done. Trim down the tube a hair, stick it all back together, and problem solved. Got all the colors back.