Ignition Coil Failure ????

[Aldo]

When I do my Aerovee mag check at 1800 rpm, this is what happens. Upon flipping the Ignition Coil switch off, there is a very small rpm drop - barely noticable. My understanding is that this is normal and my magnetron's are fine. When I switch the magnetron off (so that the engine is running on the coils) there is a drop of about 250 rpm and the engine runs rough, but does not quit. Every time this has happened up to now, I am able to get the coil rpm drop to cease by simply flipping the coil switch on and off a few times.

Any ideas would be appreciated?