I'm thinking it more likely that one of the Aes Sedai in Perrin's own camp is a Darkfriend and has been leading Masema around.Particularly with Luckers' objections to the idea that it was one of the Forsaken; the positive account is murkier, but the Aes Sedai having met him secretly is very suggestive.

Yes, Masema's crazy and easier than most to lead by the nose, but it would take a little while's direct observation to find out what the triggers are to lead him.