Thorny and strange problem: One of the backup factors loses data

One of the backup factors loses data ,and we can not located which machine is the problem. The phenomenon is to use the same pk, we can sometimes find the data, sometimes can not find the same data. Even let me locate which machine(We used eight machines to do the cluster. )

I don’t understand. Can you give us the info on your setup and exactly what was going on and what commands were used?