When trying to start laying rail from a neodyium ramp it doesnt really work.
You shift click but cant build anything.

Ive found that if I pipette any rail (normal or neodyium) and then try start building from a rail ramp it works.

So I suspect the neodyium rail ramps doesnt have a rail type specified.

Hi, sorry but I can't reproduce the bug, for me it's working as intended :/

Hello again,

After disabling my mods and testing it in a new save in sandbox Ive noticed I may have been too unspecific. My Bad.

When Pipetting a Rail Ramp you select the Rail Ramp.
You can then left click with the Rail Ramp on the Cursor to start laying Rail at the clicked Rail Ramp.

This functionality doesnt work with the Neodyium Rail Ramps.
You can pipette it, then left click, wont let you build. Instead you get some Red Cross.

Should be reproduceable now.