Hi, Thanks for the question. Several things may trigger the geometry to be re-seeded, especially if the length of the spline or the spline sections is changing. I'm not sure if this will help for your case, but one solution is to force a fixed number of Evenly and Default segments. To do this:
- Change Rules>Default to Count and use the count value to set the number of segment to appear between evenly segments
- Change Rules>Evenly to Count and set the number of evenly divisions to be used along the spline

Because the number of segments will not change using this setup, there is less chance of the random algorithms being reseeded.
I hope that helps, if you need further assistance you can send us the RailClone style on the animated spline (no need for the rest of the scene) to helpdesk@itoosoft.com and I'll happily take a look.
All the best,
Paul