In the section of the psv If it did not open at all or turn on once when it is opened from the first cause, could allow dirt to clean valve seat and disc are between. Thus causing the leak.
The psv if it had not been opened, or opening, once when it first opened reasons may cause the dirt to stand between disc and seat valve, thereby causing the leak.
In the part of PSV if it never opened or open once in a while when it opened the first may have dirt blocking between and, disc seat Valve can cause leakage.