Based on the reported behavior, this does not sound like normal OS movement. Optical stabilization groups can move slightly, but if the jump is clearly visible and occurs regardless of power state, OS setting, or focus mode, that points more toward a loose internal component than normal stabilizer operation.

The community answer suggests a possible issue with the stabilizer mechanism, such as a displaced bearing or similar internal fault. That would require major disassembly to inspect or repair, and attempting it yourself is risky.

If a used lens shows distinct internal movement like this, returning it is the sensible choice unless it was sold explicitly as faulty. Even if image quality and autofocus seem fine now, unusual internal movement can indicate wear or damage that may worsen over time.