I'm not too clear on the details, but it seems that if the miner goes into the void it discharges the OV or OD scanner in the device. Because it is coded to recharge these, it will use infinite power.
Tested by mining a bunch of things; I would often get a miner with multiple bedrock and an empty OV device.
Edit: I apologise, this is in the wrong forum. This is supposed to be in IC^2 bugs. If a mod would relocate, that would be much appreciated.