It can either have a lower resistance than it should, or if the coil is slightly moving, bumping into something, it will bounce from low readings to what resistance the coil actually is.
A build won't short if the circuit isn't hindered in anyway. So +/hot coil leg isn't touching anything but positive post/block, nothing is making contact with the coil itself, and nothing is touching the -/common post/block, with exception to the negative leg of the coil.