I had something very similar happen to some LED lamps that I had. I also destroyed the first one to fail by opening it, but I found that the main rectifier capacitor (the equivalent of the 1.8 μF 400 V one in your circuit) had failed. I also found that if I ran the light from rectified and smoothed mains voltage, it didn't matter if that capacitor had failed.
When the next one failed, I put a rectifier and capacitor from a redundant switch mode power supply in the fitting, and fed the lamp from that, and it worked without flickering and without having to be opened up.
Your LED lamps would certainly work from rectified, smoothed DC.
On the circuit, I don't see why the makers used such a large capacitor, in either voltage or capacity, for the 2.2μF 400 V. It shouldn't really need more than about 150 V for 100 V of LEDs, and the current in the LEDs is maintained by the inductor, and the frequency will be 100 kHz or so. On the photo, that capacitor looks smaller, so have you got them the right way round?
Also, the resistor are marked with two digits meaning the value, followed by a digit showing the number of zeros. So the ones labelled 514 are 510000 Ω or 510 kΩ