These speedo sensors are a bit "meh" to do and they can break up if handled roughly.

Make sure the small square drive peg isn't broken off on the end of the sensor.

It depends on the mileage if the box needs replaced.

What can happen as the miles creep up the wear inside allows bigger gaps to appear between the cogs and the also get "sharp" as well.

Anything made of nylon will start to get chewed up.

I suspect this could be the case with your drive.

By the time you pay a specialist to rebuild the box you'd be as cheap with a used one of a lower mileage.

However, on saying that, drain the oil from the box and see if the magnetic drain plug is covered with swarf. If not, perhaps someone with a bit of know can strip the box & replace the nylon drive gear for a small fee....

If it is covered in small metal shavings, I would say the box is going to fail soon anyway. I've seen it often enough.