I am using the Ultimate modpack. I haven't yet tried doing the portal spawner, but if I ever need to find the miner i can just follow its path of destruction. Let me try with the portal spawner now.What modpack are you using?
Have you played with putting a portal frame and chunk loader on the machine, for quick access after it has wander along way off? I put them on my machine and the chunk loader works fine but the portal spawner always breaks when I leave the world. It works fine as long as I stay in the world but when I leave the portal spawner breaks and I have to fly hundreds of blocks to get back to the machine.