Soldering station Yihua 899D+ blown R4 and fuse

[webgiorgio]

Hello,
I have this soldering station http://yihua-soldering.com/product-1-2-4-hot-air-rework-station-en/147660/
Used not so often, but mains connected for about 3 years.
Yesterday while I was soldering I hear an explosion from the stationary unit, which turns off. I smell the magic smoke. 
The fuse (6A t) was blown pretty violently (metal splatter all over the glass).
There was a burn in the top-right corner of the PCB. R4, 120 kOhm, 1/8W. It burned up to the point to detach both wires from the PCB and fall on the connector below.

I replaced the fuse and the unit works.
Looking at the wires and PCB traces, it seems that the 120 kOhm and also the capacitor (CL 104J, 100nF 400V) are both in parallel to the mains.
The red and black cables are the mains, the two red cables are in parallel to the red-black and goes to the transformer.

I will replace the 120 kOhm resistor as soon as I get hold of a second soldering iron.
But, what is the point of putting a 120 kOhm load across the main? 
Moreover, P=V²/R=230²/120000=0.44W, so the power rating of the original resistor (1/8 W =0.125W) was way too low!
Engineered to fail?

[webgiorgio]

Has anyone the schematic Yihua 899D+ solderign station?

[Armadillo]

The capacitor 100nF is 32Kohms in parallel with 120Kohms resistor, so the capacitor is taking the bunch of the load.
But I doubt they are in parallel to the mains but in series to the mains as voltage reducer, otherwise is a waste of energy.

[webgiorgio]

Someone one else with the guilty resistor about to burn out https://youtu.be/E7uoLxUhwlQ?t=12m49s