speedometer input shaft problem

My (old) speedo doesn't show any speed.

As part of the rebuild, I have fitted a new speedo cable. I have checked this and it is turning ok (i had the landy on axle stands and "drove" the landy, and can see the cable turning in the correct direction).

If i put a screwdriver in the back of the speedo and turn it, the speedo does show speed. My thought is that the (plastic?) input shaft is worn so is not connecting with the new cable (but the screwdriver is big enough to connect with the plastic). I don't have another speedo cable to play with.

In the ideal world, i would replace the input shaft, but that looks difficult. I could shove some glue down the hole and push the cable in, but that feels like it might cause more problems that it might solve.

Anyone else had this issue?

I would try putting a bit of epoxy in the drive square but put just a smear of Vaseline on the cable end push it in and leave to set. If it works good, if not you will still be able to remove cable.