I know that moving Sentry’s aren’t possible (besides the gamemode Apocalypse), but you can animate sentries, so that’s what this is below.
My first one was too ambitious. It included a splitting and converging path and a button (door) that would change its direction from ending the game to resetting the last position on the path to the start point. (It didn’t go well… every sentry place would eventually be on at the same time.)
Feel free to use this as references or guides if you are trying to do something similar to this. And trust me, getting the small path down and working first is better than making the full one work.