Toto je známy bug.

If Arngeir gives Arcwind Point as the location of a Word of Power, finding the word wall and learning the word may not complete the "Find the Word of Power in Arcwind Point" miscellaneous quest objective. The quest marker will remain in front of the word wall. The word wall located at Northwind Summit completes this quest, but only if it has not been previously found.[1]
If playing on a PC, the console command SetStage FreeFormHighHrothgarA 20 can be used to complete the quest, however Arngeir may give the quest again.