Check this with just IV. Issue doesn't persist. There's some other mod causing this, and unless we can figure out which mod is mucking with arrows, then there's nothing I can do.

It's "Iblis Headshots" causing the issue
It creates a thin hitbox at the centre of the head
which projectiles probably hit when fired downwards
this occurs exclusively in the latest version of IV's presence

Fixed in V19.15.4. Likely due to these changes: b554caf