The trust problem is the idea that someone may in fact have had a spiritual experience, or a be in possession of revelation from God, yet there is no way for an interested observer to determine whether or not the person claiming revelation is telling the truth or not.
How can we have the same faith as the patriarchs, who walked with God, had visions, saw angels, and experienced prophecy and revelation? How can we trust the (chain of) people who tell us that these things really happened? Where is the source of information we can go to to know these events really happened, today? (Standard answer is, the bible).
When the PA stated that they are in possession of revelation, revealed knowledge, they may be asked how you as a third party can verify that they are telling the truth. After all, you may propose, the holy man of any religion will claim to know the truth; where is the source of information you can go to in order to determine which holy man (or denomination of Abrahamic faith) is telling the truth? (again a standard but often overlooked answer is, the bible).