Sounds like the hold winding on the coil is not working Check as per Stevesee and also cheek the coil winding ( the thin wire)
for open cct
I agree on this one, the coil that is connected to the EOS is working, but the hold coil is not. flipper goes up, opens eos, then there is no hold coil working to keep it up, so as soon as the eos opens the flipper drops down and the eos closes so the coil energises again and then goes back up, opens eos, flipper drops and so on. 
+1. Check the coil. hold coil will be open circuit.
