Insight
Adventurer
One way to engender more "social interaction" is to deconstruct the published adventure and string it back together with a semblance of plot that will, by default, cause some interaction possibilities.
Other ideas:
Perhaps the PCs aren't the only ones interested in the tomb.
Perhaps someone has a vested interest in seeing them fail.
Perhaps the PCs find a trapped noble insisting in being escorted out of the tomb before the PCs continue with their dungeon crawl.
Better yet, perhaps the noble can be convinced to help the PCs.
Other ideas:
Perhaps the PCs aren't the only ones interested in the tomb.
Perhaps someone has a vested interest in seeing them fail.
Perhaps the PCs find a trapped noble insisting in being escorted out of the tomb before the PCs continue with their dungeon crawl.
Better yet, perhaps the noble can be convinced to help the PCs.