Switching power supply only works when warm
Could be a bad chip, or could be a bad solder joint. Easy to find out if it's a bad joint- just take a soldering iron and reheat all of the joints and leads in that area (including pin 6 on the IC- solder looks a little sparse there). Use a fine tip on your iron, and add a little flux to aid in the reflow (a tiny bit of added solder might help too, but not too much). Use as low a temperature as you can and don't heat a joint to the point that other joints unsolder themselves. Start with the IC, and test the PS after things cool off. Then move on to other joints, one at a time. Moderation!