1991 Toyota Corolla

I have a intermiting problem with my starter. My car is a toyota corolla 1991.

I do delivery with this car and let's say that about once every 60 deliveries me starter fails to engage, I could hear the clicking noise, but it's just dosent start.
then after 10 to 15 minutes of just trying to turn the key to crank it suddently strats again and is good for another 60 to 80 deliveries.

i have allready change the starter ( rebuild starter), and I still have this intermiting Problem?

I have also change the negative baterie cable. Still have the same problem

The last time the starter was not engaging i've check my batery with a volt meter and it has 12.6 volts. And when the stater works then the batery has 14.3 volt.

I'm running out of solutions.