As a teenager, I used to suffer from Sleep Paralyses.
This is a terribly distressing condition where, upon waking, a person is unable to move. I would wake up and literally feel as if someone was crushing me. It was a terrifying experience and over time it began to happen with increasing frequency.
My Rov mentioned that I should check my mezuzahs. I agreed and asked my Rov to come and check them himself.
The Rov began with the mezuzah at the door to my room. Through the words b’shochbicha u’vkumecha (when you lie down and when you get up) there was a line of ink that was missing!
The Rov then proceeded to check the rest of the house’s mezuzahs and found that they were all invalid.
With the procurement of a kosher mezuzah for my bedroom door, my condition disappeared entirely. There is no natural explanation for my instant recovery; only a spiritual one.