Hi,
The only reson, I can see, why the solder does not stick in a certain spot is becuase that area hasn't been cleaned enough.
"where it will stick to the iron like a magnet and refuse to return to the board"
Ya I get that sometimes. Solder is attracted to heat(soldering iron), so (if you haven't already) hold the soldering iron at the end of the pin, or far enough away from the soldering area, but still have enough heat to melt.
Is your boards held level? Do you use a scratchy pad to clean the board?
Hope this helps,
D.J.