Camera rail and camera error? after "save level as'

I have a world-partition environment, packed with splíne-based PCGs, in which I created a camara rail and camera to make a short movie - very basic, one sequence. The rail starts in one region, and continues in the adjacent one, and all works fine.
Due to some issues that may be related to these splines, I removed them, and used PCG-volume instead. No issues with the sequence…Swtiched raytracing off (because the issues had to do with RayTracing). Saved the level under a different name, removed the PCG volumes and re-created spline-base ones, one region at a time. But now the camera rail and camera are painted red in the sequencer, I can start the sequence but nothing changes. No error is shown so Im in the dark 'what is wrong.

I’m on 5.4.4

When something is red in sequencer is means its lost is binding to the actor in the level for whatever reason. You can right-click it in Sequencer and go to Assign Actor at the top of the menu, then pick your rig rail again to re-bind it.