When an interface name on a switch or router is renamed, this is not automaticly discovered by PRTG. When we run a auto-discover, the interface isn't renamed, but a new instance (sensor) is added with the new name. Therefore there are two sensors with the same interface index number. When removing the old interface, we loose the performance history.
Is this a bug? Would be prefeable that PRTG wuold rename the interface, and not add a new one.