Two weeks ago, I had an Asus X555 that had no backlight when on battery. But it had steady backlight when on Charger. Then, I replaced the coil with a good one (100uH) from another screen. Then, the problem got fixed meaning that it had steady backlight when on battery.
However, the customer discovered that the backlight fluctuates when it is on battery and the battery charging level is under 50%.
What component does cause this problem?
What should I do now to fix it? Any similar experience?

ok, so the zener diodes are fine.
Thanks @eccerr0r​...

there is no visible sign of damage or burning on the zener diodes and the board.
I tested the Zener diodes on board using the diode mode of multimeter. however, I do not know why my multimeter struggles to apply voltage on some of the zener diodes. On one direction, it shows infinite resistance. but on the other direction, sometime it shows 0.6v and sometimes it shows infinite resistance.
I used to use this power supply for voltage injection on laptop mainboards. I do now know why Q1 and Q2 got shorted.

Dear members,

I have a linear variable power supply with unknown brand name that I used for voltage injection.
Then it failed. I discovered that its transistors (Q1 and Q2) are shorted.
In addition, I discovered that its zener diodes are defective.
I can replace the burned transistors.
But I do not know the model of the zener diodes. the model number is not marked on the zener diodes.
Therefore, I cannot replace the zener diodes.
I do not want to test the zener diodes in a test circuit to discover their model or value.
no schematics are available...