When you use a techreborn machine it starts showing a working animation on the front when its done, it keeps on going, even through reboots.

Is this all of the machines, or a specific one? Do you have any upgrades?

No upgrades, I have seen it in three machines, have not tried more.

For me too, grinder, compressor and alloy smelter seem to work continuously (red color, animations). But electric furnace does not. (All 4 have overclocker upgrades).
Modern Skyblock 2 pack