If the old one read correctly and gave 8 pulses per revolution,
And the new one gives 16 pulses per revolution, then the new one isn’t the one you need….you have the wrong part.
So either get the right part or you can get a little electronic box of tricks that will adjust the input pulse rate of the box to the output pulse rate that you want.
No I’ve got no idea where you might find one, but I do know the such things exist.
I’m sure our esteemed and knowledgeable friend Airportable, will be along soon with some light to shed on the matter.
"Keep calm, relax, focus on the problem & PULL THE BLOODY TRIGGER"