Hello,
I am using the latest version of Dynamic Crosshair (9.3 as of me writing this) but the issue started occuring on 9.0 (I believe).
Basically, the crosshair looks vertically squished/warped when I fullscreen (technically maximize, I don't use Minecraft's own exclusive fullscreen mode and instead use macOS's fullscreen method) Minecraft on macOS:

Compared to a maximized (or any size, really) window:

Like I said, I am using macOS (14.7), Minecraft 1.21.1 on Fabric. The Dynamic Crosshair configuration is the defaults. Nothing relevant as far as I can see in the log.
Using Minecraft's exclusive fullscreen doesn't create this issue, but it also doesn't allow me to half the Retina resolution (a feature of Sodium/Sodium Extra), which I use for better performance w/ shaders.

UPDATE: The issue also doesn't happen if I disable the Half Resolution option from Sodium's settings and use macOS's fullscreen, so I believe it's related to the resolution switching? For reference, the full resolution is 3024x1890 (on macOS fullscreen, issue doesn't happen), 1920x1200 (on Minecraft fullscreen, issue doesn't happen), and 1512x945 (on macOS fullscreen with Half Resolution, issue does happen)

No problem! Let me know if there's anything else I can do to help.

Ah, another case of "what is the central pixel on a display with an even amount of pixels", just the opposite way. I think I know why this happens. Thanks for the report!