[UPDATED ... thanks to Benefactor]

Dawnguard Quest: A New Order (Main Storyline, Quest #4)
Sub-task: Recruit Gunmar

Problem: Gunmar's location was apparently implemented by the coders as a radiant quest (read: random location). The problem I encountered was that its possible for the radiant logic to place him at a random location outside of mainland Skyrim, and when that happens the quest marker for him fails to appear for the player when they acquire it at Dawnguard Castle). I spent several frustrating hours kicking around skyrim, and reverting to earlier saves to no avail, until someone suggested hopping on a ship back to Solsteim (Dragonborn DLC), to see if the randomizer had placed him there (which it had, in my case).

Recommended Fix: If the radiant quest logic randomly selects a quest location in Solsteim (Dragonborn), a quest marker should be placed on the docks of Windhelm, to help clue the player that they have to leave the mainland. Without said marker, it is difficult for players in mainland Skyrim (Dawnguard) to know how to continue the main storyline.

Info:

* Skyrim version: 1.9.31.0.8

* PS3 = 120 gb slim, with 18gb+ freespace

do you have dragonborn installed? if so he could be on that island.

I'll be gobsmacked if the coders enabled that to occur, but I'll try it. Thanks.

UPDATE: Ok, good call ... I went to the Isle of Solsteim (Dragonborn DLC) and for me his random location turned out to be Horker Island in the far NE.

Thank you for the tip.

I'll revise my bug report at the start of this thread to report the successful workaround, and suggest that a quest marker also be placed at the windhelm docks if the radiant logic places Gunmar in Solsteim.