I can't really recreate this problem to see what is going on, since my save file doesn't have any log entries for this quest and "False agent" starts right after sleeping twice. Even before i speak with Vehlist again, now that i check it.I already rescued Vehlis snd she is back at the orc camp but the mission doesn't show up as finsihed and I can't start the next one (called False Agent in the walkthrough)
Maybe one of the side content blocks the progression somehow? I'm not familiar with the code.