https://github.com/Tubbles/Construction_Drones/issues/21

There is no error log.

Rails and Drones collide with each other. Rail track cannot be placed where a drone is and drones cannot cross any placed rails.

That is my observation true, drones treat railway as real entity that blocks their path finding.
However, it was all working before factorio 2.0, something inside factorio upgrade must be buggy towards this great mod.

It seems like the collision masks are not correct, I will fix this tomorrow probably :)

I had problems specifically with the old rails. When you build an old blueprint, the bots try to build legacy-rails and get stuck in them, and then an error occurs.

This bug has hopefully been fixed now in 2.0.2. If the issue persists, please open a new thread here on the mod portal or on the github page, and make sure to add the following:

• factorio-current.log
• A general description of how the bug happened
• Any error messages
• If possible, consider uploading a save file where the bug is reproducible