yeah more or less. without getting all technical and put simply. the power produced by the stator and flywheel magnets is AC current which means 50% is a positive charge while 50% is a negative charge. this is rectified in the RR which converts the negative charge to positive giving a steady DC current.
the test the OP has done [the one we all do when issues arise in the charging system] shows up a fault in one of the stator feed wires. because two work perfectly but one is 50% down on power. this means half the AC current going down that wire is disconnected somewhere.
all you can do is trace the wires back to the coils they exit from no further. if the break is inside the coil windings your stuffed. it is a good replacement you need.
however it is possible and quite common for vibration or foreign object to damage or cut one of the wires from the last coil to the feed wire.. if it has you will see it. if there is nothing to see it cannot be repaired.
had exactly this happen to a bike before in that case a small screw from he trigger plate had come loose and cut one of the insulated copper wires where it joined to the feed wire once re-soldered it was fine.
note. if you look at the photo Duc kindly posted you will see each of the feed wires has two wires connected to it one is + the other is - you will also see they go down the side of the stator to the bottom of the coils this is where they break or where they join the feed wire.
all I am suggesting is carefully inspect all the wires you can see in case one is broken. the areas highlighted by red circles and yellow arrows.
Last edited by yorkie; 1-2-2020 at 5:30 PM.