One thing to keep an eye out for (mark and I were just talking about this, and I’ve hit this problem a couple of times).
If your 5v power supply is a bit dirty, and sometimes drifts above 5v, you can get weird glitching on the leds. My theory is that what is happening is that since the data pin signals are 3.3v output, as long as the WS2812 chips are getting 5v power, it can differentiate between high and low. However, if the WS2812 chips are getting, say, 5.25v power, it becomes a lot more difficult for it to catch those transitions (or reliably catch them).
The solution is probably either a level converter, which I haven’t tried yet, or play a variety of tricks that drop the input voltage to a bit below 5v. (My favorite at the moment is plugging the dirty 5v power supply into one of these - https://www.adafruit.com/products/1385 - which spits out about 4.75v when fed 5v).
It’s included by FastLED/controller.h. I think the problem is that the RFduino isn’t an AVR, so the avr/ subdir isn’t included in the system path when I have the RFduino board family selected in the Arduino IDE.