I eventually figured out how to fix this issue so here it is if you run into the same trouble:
*The problem seems to be related to maps that are removed from the mission after tasks are assigned to it.
*I am almost certain I manually deleted all the storyboard entries before removing the map itself but doing so, and not just letting the map deletion cover this, is still a good idea.
*The map where the problem began was a duplicated map (the return to space after the ground section is complete).
*When I tried re-creating the map by name (and I typed it in) this did not help but when I re-duplicated the map from the original (meaning the initial space map that the mission re-used) where the name was generated automatically, the problematic dialogues were returned to the storyboard where they could be removed manually. This time it seems to have taken.
Anyway, hope this helps anyone who also runs into this.
First, if Cryptic stops by they'll need your mission's short code. Always need to include that so they can go take a look.
Second, when you test in the Foundry, have you tried hitting "Reset Map." I remember some instances of testing a map and having dialogue showing up where it shouldn't, but then I hit reset map and it works like it should.
Also, have you tried doing a test publish? Sometimes things are fixed in the publishing process.
The Foundry Roundtable live Wednesdays at 7:30PM EST/4:30PM PST on twitch.tv/thefoundryroundtable "I would rather take a chance on getting a change made to the game through positive engagement than know for sure that I got a change made by complaining" -drogyn1701, May 14, 2014.