Enemies don't follow pathnodes...

[Phoroneus]

If memory serves me right, ShowEnemyPlayerPosition gives the monster a snapshot of where you are at the time it's called, rather than a permanent view of your location. If you call it right at the start, the monster will run to your spawn point in search of you. If you're still in LOS or audible to the monster, it'll continue to hunt you, otherwise it will search briefly and then become confused and just stop activity (unless it has another assignment to get to).

Your best bet to have a monster constantly chasing you is to give it a full nodemap (around and between all obstacles and anywhere you might put non-breakable obstacles) and then repeatedly call ShowEnemyPlayerPosition. If your intent is only to have the monster chase the player, then ShowEnemyPlayerPosition is probably more than you want, since it'll run faster than the player can get away from it, and will ultimately kill the player if they can't get to safety in time. There are a bunch of other methods to get it to follow you menacingly without it actually killing you, but they're a bit more complicated.

Of course, the "cutting-corner" problem is the first thing you should check for, since that'll confuse the heck out of the AI.