Hi all, sorry about late reply. The prox sensor is honeywell 922AA1Y-A4n-L. We found the hydraulic motor mount was not very tightly mounted. Or at least I think that is what it was. We also got the distance between the prox and the gear teeth at about 13/1000" inch according to the gauge we used. And it had been working correctly for the last two days. So keeping my fingers crossed. FYI, an old CPU board counts the input pulses from the prox to calculate the travel distance. Again, thank you so much for all your inputs. I have printed out all of them to try out if fails again.