I have a relatively new IQ-X (8months old) and it developed an issue recently. The tailight connected to it (Secula) will "flicker" corresponding to road vibrations but it appears to be mostly "off". So when I hit a rough patch of pavement it will flicker a bit. After checking all the wiring for a poor connection, I discovered that "pulling" the output cable forward near where it exits the headlight will make the taillight stay on, until i let go.
So i think that indicates that the output wire is loose or has a poor connection inside the IQX. Its worth noting that the cable is not pulled or otherwise improperly installed. Also a note that the headlight function works as expected.
Has anyone else had this issue? Makes me nervous about getting a replacement in the same flavor.