I can confirm that this does happen. Although, I do not get a crash when doing this quest, this loop is annoying. The only way out is pressing escape, but the next turn it is up again. Here is a fix for the problem.

https://dl.dropboxusercontent.com/u/75549875/Fallen%20Enchantress/QuestFixes/Quest_Slavers.zip

The changes are as follows:

In objectiveID 0 -- choice dialogue below (the bolded was 1, it should be 0)

            <QuestChoiceDef>
                <Description>I'll return later.</Description>
                <NextObjectiveID>0</NextObjectiveID>
            </QuestChoiceDef>

The next change is in ObjectiveID 3 -- choice dialogue below (the bolded was 1, it should be 0)

            <QuestChoiceDef>
                <Description>I'll return later.</Description>
                <NextObjectiveID>0</NextObjectiveID>
            </QuestChoiceDef>

This returns the dialogue to when one first encounters the slave caravan. The only quirk that happens now is at the second I'll return later, it will move the location of the slave caravan. (I do not know of a way to prevent that from happening, but there you go).