That post did qualify as your second, so you've passed the first hurdle.
D strings seem to have caused more than their fair share of problems here over the years. It isn't the sort of thing that is easily found by the forum search tool (since it would ignore "D" as being too short), but you can find a number of possibly relevant discussions using Google search and putting in the following search string exactly as written below:
"d string" site:classicalguitardelcamp.com
Classical Guitar Forum.
"Experience is something you don't get until just after you need it." - Steven Wright