I want to know what do you think?
What was probable cause?
Before that, for last 2-ish years I must replaced 5 LED bulbs.
No other symptoms.
Right before failure, one or two LED bulbs started blinking.
I heard "scorching" sound.
And smell of burned electric/electronic (isolation).
Then I disconnected all circuits and opened all surrounding boxes...
Over-current breakers or RCD/GFCI didn't tripped.
Extra photos:
(ignore temporary jumper - fixed now)
A loose connection creates heat, but doesn't draw additional current. Assuming nothing changed on the load, the breaker wouldn't see excess current and would have no reason to trip. 16A is plenty enough current to get a bad junction toasty hot without tripping the breaker. Breakers protect from shorts, but can't protect all faults.