Elgar’nans fade trap glitch

I’m escaping his trap while Solas confronts him, and after making the bridge and destroying the blight, a monster is supposed to appear so that I can remove the next blight that isn’t red activated yet. However no monster shows, so the blight is still inactive and cannot go through…

anyone has an idea how to fix this? I restarted the game 5 times, turned of my set up, reloaded from a previous save to start over the whole quest and still no monster to active the blight…