At my previous employer when I was not installing and repairing microscopes and imaging equipment, was part of a team developing a piezoelectric product line (chips not stages). The reasoning behind this was that other business units (BU) used piezos from a variety of manufacturers. Our first task was to design a drop in replacement for another BU, because that was the single most expensive part and it often failed.
A large part of the product development involved accelerated ageing, in a high temp, high humidity environment at high voltage. This simulates normal use over several years. In a car’s fuel injection system, the piezo is hermetically sealed in a steel cylinder with an inert gas, and lasts many years. However in a stage, the piezo element is either comprised of many individual chips glued to form a stack wrapped in Kapton tape or it is a single large chip sealed with an epoxy. These types do not last for more than a few years, with the later lasting slightly longer (PI uses the later in their stages). The environment degrades them over time.
We used a laser interferometer, which has much higher resolution than a microscope to test them. So it might look “ok” and the stage might move, but it is not that easy to tell if it is good.
Once a microscope customer dropped a PI stage. It looked “ok” and still moved. However the individual chips were cracked and the flexure was damaged. It had to be sent back to PI for testing and replacement. Also, keep in mind that new, they have shipping brackets and are vacuum sealed often with a desiccant. It is likely that small parts such as the original packaging and shipping bracket have been lost over the years and that any secondhand seller is not going to vacuum seal it.
Also, the stage and controller are matched and are not interchangeable as the PID of the controller is tuned to match characteristics of its stage. It is possible to re-tune, after a stage is damaged or for a different stage, but not a simple proposition.
I would recommend you send any secondhand stage purchased back to PI for testing and repair (same if they already have one which is malfunctioning). Olympus probably won’t be of much help as its an OEM product and also these are older discontinued models. This needs to be accounted when you consider the cost. It is worth considering to buy a new, non-Olympus branded stage instead.