The innjection pump actuator responds at hydraulic position sensors too. Seems to me your problem in in commandin the actuator, not the pump and not actuator itself. To separate the problem try to disconect electrical coupling beneath the lift lever (beneath hyd.distribuitor) and observe general reaction. This Hall sensor is not such a reliable part.. Then do the same for the other sensors; this is an empirical way to troubleshoot..
Let me know about progress.