Electronic ignition issue
Both the crank and cam sprocket are keyed. I cannot see how an all steel cam drive with only 3/8" of chain play could slip. I'd recommend you get a second set of eyes on the thing.
Look carefully for more key slots in the crank sprocket. You may have an "advance / retard" cam drive set which has at least THREE different timing marks on the sprocket
I don't know what the below sprocket fits, but they all work similarly. You use which keyway you want, but you also must use the correct mark.
Some sets have a dot for zero, and a triangle and square for the advance/ retard, others have "O", "R" and "A"