I have a weird problem with my old 3D printer, it is a Prusa/Mendel type. When I print a 20 mm cube, X and Y are correct, Z is resulting 16 to 17 mm. I have checked the correctness of the movement on Z using the manual controls and there are no issues.
I played a bit with the layer thickness, I have a 0.4 mm nozzle, setting the layer height to 0.12 mm (normally is on 0.16 mm) but no changes in the result. I am printing PLA on a cold bed at 180 °C without any other particular defect.
I would appreciate some direction on how to solve such problem.