Is the meaning of wajada in 18:86 Quran incorrect?

Till, when he reached the setting-place of the sun, he found it setting in a muddy spring, and found a people thereabout. We said: O Dhu'l-Qarneyn! Either punish or show them kindness. First of all there's no ONE place where the sun sets since the earth is spherical. Second why do tafsirs of this verse add their opinions about what it means. Lastly, Muslims claim that since wajada can mean false or true perception,Dhul qurnanyn was clearly falsely perceiving the sun setting on the murky water. However the preceding verse clearly states that this is the place where the Sun sets. So how can he be wrong when he is in the right place ?