Over fill would mean to much water in the drum.
So no problem with the water getting in.
From my under standing is the tube that comes from the drum up to the controll panel is how the machine senses the water level.
The new controll panel being fitted and the problem remaining rules out a fault with the panel.
If you mean lime scale in the solenoid valves,then they might not be shutting properly,but then they would be letting water in all the time and filling the drum even when the machine is not being used.
I would check the tube and pipe from the bottom of the drum that goes to the controll panel.