There are definitely some glitches related to using the trainer and completing tasks, but I have read about this glitch before and by people NOT using the trainer.
Apparently, if you try to place all 6 seals at once from left to right, the gate will glitch out. Personally, I've never encountered this because the only time I've played through the game, I placed them as I got them.
So did I. I would play a temple, get my seal and giddily hurry back and place that seal as fast as I could.
It wouldn't surprise me at all if it's a glitch in the game and/or some kind of bizarre bad alignment where the game and the trainer just crossed each other the wrong way.
At least I know I'm not the only one with the issue.
At least these trainers are WELL documented, including any potential personality issues of which a few of those cheats clearly have.
All I can figure is I accidentally left something on and the game didn't like it or who knows what. Oh well. I KNOW I earned it and beat all six of those damned temples and I kicked the game's butt.