When placing belts sideloading onto other belts with colored rails and black, arrowless belts, the belt sprites seem to be layered weirdly.

Belts sideloading to the left or right sides of a vertical belt appear to be above said vertical belt.
Belts sideloading to the top of a horizontal belt also appear to be on top of the horizontal one
Belts sideloading to the bottom of a horizontal belt appear to be on the same plane as the horizontal belt, like I would expect.

I would post an image, but I cannot here, so you will just have to put some belts down in a cross shape to see what I mean.

That's a vanilla feature of belt sprites that's been part of the game since 2018.
Here's a comparison screenshot.
Here's the FFF that talks about the redesign.
Everything is working as intended.