Talk:Stalker/@comment-50.135.157.64-20151106015723/@comment-192.76.8.27-20151108001940

I don't know, but at a guess, it's your mission selection. Stalker can appear in any faction mission, but Zanuka and the Grustrag Three are limited to levels where their own faction is present.

Have you by any chance been doing a lot of Infested content lately?