Is it the quality problem that fog lights are with moisture?
No, this is a normal phenomenon. Fog lights are designed to be waterproof, but it is not completely sealed. There is a specially designed ventilation tube or vent for heat dissipation in the back of the light.
Note:
If the fog light is seriously leaky, please check it first if the fog light is cracked or otherwise damaged, and then check if there is a problem with the sealant of the fog light housing/lens, because the sealant will age as time flies.