Please elaborate the reasons for failure of electronic ballasts?

The less serious faults are based around converting AC to DC and smoothing it. The smoothing capacitor dries out and looses capacitance allowing a mains frequency ripple to appear imposed on the HF output, this may cause lamp flicker. The other issue is a failure of the oscillator circuit to start promptly at switch on, this causes large currents to flow in the primary of the transformer and damaging the transistors in the oscillator, bang, the in line fuse blows. These things operate on the edge, they fail at the least reason, but when they work, they are great, they will also run on DC.

I think it is not a matter of generalization on the basis of the circuit exact possibility may be reasoned out.