Hey there FrankTV.
Quick question: did you upgrade the superX to the latest firmware (1.07)?
I did, and while I didn't experience what you're seeing there is reference to a solid yellow indicator in the 1.07 release notes:
4. The processing to magnetic interference under GPS ATT mode
a. Ferromagnetic interference, LED flashes red, copter cannot be armed.
b. Weak magnetic interference, LED in solid yellow. Copter still can fly in a transiently interference, but SuperX works under ATT mode instead. If the interference is continuous, we suggest to land the copter. If there is interference before take-off, motor can’t start under GPS ATT mode.
Not sure if this is relevant, but thought I'd share.