Skyrim PS4, how do I fix the Quest bug?

Quest line: Dawnguard

Quest: A new order

I have to recruit 2 people, a woman and a man. I have already recruited the woman, but the man is not shown on the card. Saw a Youtuber where he usually stays for this quest and then went there (crystal gallery cave), but he is not there. Now I can't do the quest and I'm not getting anywhere. Does anyone have a solution?

Known problem. If Gunmar can't be found in Skyrim via the quest marker, he is on the island of Solstheim from the Dragonborn DLC. There he is then I mean on the east side on an island with a Horkern.