https://www.dropbox.com/s/fy5xm8lmd3....jpg?dl=0&s=sl

This supply came with a 2 foot 9W strip light of LEDs. After 1 week it began flickering badly. 240V AC in on the right. The circuit outputs 75V DC on the left, with a 3.5V AC ripple on it (with the 100uF capacitor included, which I verified is ok). With a 680uF capacitor in its place, there is no visible flicker.

What's likely to have broken in this circuit?

What's the chances of it lasting if I run it with the larger capacitor?