I had to look up Montanism to make sure I had the correct view of it and yes I understand your sense of danger. Old Montanus himself would go into strange flailings and convulsive states saying stuff that didn’t always bear up under scrutiny. The I looked at the behaviors of those of the Bible who uttered real prophecies...their behavious were rational often times pleading and they didn’t always deliver good news. Yet their prophecies were 100 per cent accurate! Always!
Some of the prophecies have not been fulfilled (e.g. destruction of Damascus); others were conditional, e.g. Jonah and the destruction of Nineveh, but they repented.