Some of the aftermarket cables need to be lubed with lock lubricant, ptfe , like repco or drivetec. If not lubed they don't last long, also they really need to be inserted fully or they fail quickly too. I have had hit and miss longevity from the aftermarket ones about $20aud. I got a spare ome (by far a higher quality item) but the drivetec seems to be good for a few years now. I think the ome cost $50-60 from amayama, they can last 30 years.
I use to use a garmin satnav which gave satellite speedo readings, how accurate can't say for sure, pretty close. Before I got a fangled phone with the lady interrupting the tunes by giving directions..
I am usually one of the slowest in my hj75 anyway!