If you create the default mesh for a turnout/junction with the attachment points, you need to ensure that you have at minimum 3 attachment points for each track.

If not you can run into serious problems, for example the junction is broken or the track spline looks not like it should.

In the following picture you can see what’s happen with my junction asset.

(left) junction damaged due wrong angle, (middle) straight track is not straight, (right) the right turnout is now an left turnout

The direction (angle) of the Y axle is really important. The angle of attachment points within the track is irrelevant. The Y axle of end attachment points must point in the direction where the track will continue. This is also very important for the junction attachment point, because this is the end of the straight track. If this is not correct, the junction will look like some of them above.