yeah, it's because the internal resistance of the capacitors that are used on the controller are near 0 ohm when unused/uncharged. the 2nd time you plugged it in, it's likely that there still was some juice in them left, so that's the reason it didn't spark the 2nd time.
If you swapped the poles on the batteries, the spark woult be quite a bit bigger..
Well i order the rong pinions 2 times, and hey dont make the right pinion so i cant use the truck. If i want to make it work right, i have to buy a 8s with the standard size shaft, and buy new batteries. Im just going to returning everything, and selling the fu*king truck, unless the fiegao 12s has the 1/8 inch shaft.