EL components blinking unexpectedly

I am new to Arduino and using EL components, but have roped in some help and advice. However, we've come up with a problem. I have connected an EL shield to an inverter, and Arduino Uno, with a simple bit of test code, which I believe should light up any EL component solidly. With one of the small (3x5cm) EL panels it creates a solid light, while with others (the same size or larger) it causes them to blink. Also with one of the 1m length EL wires it lights up constant, and with another it blinks.

Any ideas why this is happening? I want to be able to create Arduino effects (fades, pulses etc) but if I can't even rely on a stable signal I'm not sure how I'll be able to achieve the desired results!

Thanks in advance