Why is my fov randomly changing when i look up and down?

So I changed my FOV once and it worked, but whenever I looked up or down it just weirdly zoomed in. I reversed the changes in the FOV to default and it’s still happening. Any idea why? (first person)

Are you positive the FOV is changing? As in the numerical value of the field of view is changing?
If not, it could be that your camera is not on the center of your pawn, and so when looking up or down, the distance from the floor changes