Here is a great case of reporting a problem even though it might have been resolved by some luck!
Thank you @renm for the problem report - this one was super important to catch!
Apollo’s heatbed started reporting higher and higher temperatures, and would not start a print. It wasn’t heating really… but even after being set to cool down reported high temperatures. This is a great reason to abandon a printer and use the one next door! If you had gotten lucky, it’s possible you could have gotten a print started, but you made the right decison!
When I arrived, the heatbed was reporting 325 degrees C, but was set to 0. 
There was no heat rising in the air above the bed… and that is not possible for these heatbeds to reach in open air. So I carefully touched it and it was room temperature. Moved it around a bit and it dropped to… 25C? 
This is an electrical problem. I shut it down and unplugged it for service.
Good news! This failure was due to an incorrect service or install, and won’t happen again. The other two printers don’t have this issue. Here’s the problem, AND the root cause in one pic:
The heatbed thermistor wire at some point got trapped between the bed carriage and the printer’s frame - probably leaving an artifact on someone’s print in the process. When trapped between metal parts, it wears away the insulation, and eventually grounds out the thermistor with nearly zero resistance read!
The cause? Bad wire routing! There is a small channel to safely route this wire with the main heatbed wires in the protected sleeve. The fit is tight, and the install is fiddly. At some point, we remounted this bed with the wires run incorrectly, eventually leading to this failure.
We had the parts in stock, so I proceeded with the repair, this time with safe routing:
(This is actually missing one piece - the protective sheath gets anchored by tension in the printed bed connector piece. But that hides the issue from the camera. 
)
Thanks again Ren for a timely problem report - these machines are tough, but they can wear in unexpected ways!