Improper Ground

Installer did not tighten set screws on coupling,but, there must be some type of current flowing n the E.MT., either fault current induced current or someone decided to use the E.MT. as a neutral.

when there is screw loose heat will occur then the joint will damage

The conductivity of die cast zinc connectors is about as poor as the conductivity of the steel EMT-about 10-25% of what a copper wire has. Looks like a great arguement for always running a green ground wire inside every conduit instead of relying on the EMT. I spent 13 years maintaining a 237 unit high rise apartment building and found many, many pulled apart EMT connections in the various shafts running up through the building. Service people would step on the conduits while repairing plumbing, etc. in the risers and that would leave kitchen receptacles un grounded as well as others in the units. Maybe its time to revise this short cut wiring method that works but leaves room for problems to occur over the life of a building. A lot of these problems with EMT could be prevented by not allowing conduit to be routed across a riser as the shortest route to an end point. All EMT should be close to a wall, etc. Maybe the 1951 code allowed this and it never happens today but.............