I've been in the habit of making vias on homemade pcb's by putting the leg of 1N4148 diode into a 0.5 mm hole, cutting it off to length and soldering both sides.
However, now my led controller broke and I traced the problem into a broken ground via. On closer inspection, the wire has separated from the solder:
There was about 2 ohms of resistance between the wire and the ground plane where it connects. During operation, there has been about 1 ampere of current going through it for a few hours each day. The device internal temperature stays below 50°C at all times, and has always been stored and used indoors.
Are there any obvious things that I'm doing wrong? I doubt it is a cold joint, because a bit of solder remains also on the wire.