The bug is quite simple; Unlike in previous versions, the crosshairs in the 1.13 snapshots are unbalanced (see attached picture for proof/example).
Environment
My environment is a Windows 10 operating system, though I do not use the Windows 10 version. I use the Java edition (I'm very sorry, but I could not identify my java version without tearing apart files and downloading lots of things).
Please do not mark unreleased versions as affected.
You don't have access to them yet.