Loose cable to your temp sensor on the bed. Almost surely just loosen and reinsert the two sensor cables (the thinner 2 cables) where they connect to the heated bed.
You might be able to get to them in the back but probalby you have to remove the glass, remove the 3 leveling screws and take it apart. An experienced person can do all this in 5 minutes but if you have never done this before reserve 20 minutes.
The replaced heated bed and/or sensor are original? I heard in Ultimaker forum community that temp sensor is fragile, and you need to take care when deal with it, for nozzles or bed. Check some youtube videos to know how to change this sensor without brake it. gr5 (expert user) has some tips to change it, ask him if you still in doubt.
The replace bed and heat sensor are originals and not half a year old. I checked the wiring, which is fine.
What I dont understand is the context of the stepper motor for z axis and the temp sensor…nevertheless I checked with the supplier of the heatbed and I can change it.
Hope that will help.
Thanks a for your time and help!
The sensor is tough as hell. You should be able to drive a car over the heated bed and the only thing that will survive is the temp sensor.
Much more likely something broke at the connector to the board. You said you checked the cabling so the second most likely thing is you need to reflow the solder. Just heat up the solder under each of the 4 connections where that screw terminal block is mounted on the board.
The reason it is associated with Z movement is because something is soooo loose that just the movement of the bed up and down or the changing of angle of the cabling to the bed (even though it’s screwed down) is enough to make the wiring disconnect briefly.
You can power off the machine and hook up an ohm meter to the temp sensor cable where it connects to the circuit board and measure the resistance. It’s supposed to be about 108 ohms at room temperature. When it’s bad it will be over a thousand ohms. But it’s so much easier to just take the bed apart and reflow the solder and remove the 2 temp sensor wires and screw them back in again tighter.
gr5: “The sensor is tough as hell. You should be able to drive a car over the heated bed and the only thing that will survive is the temp sensor.”
hahaha… nice! I was postpone switching my UM2 nozzle to olsson block because I thought it would be a headache to change that temperature sensor. Now I just need to find someone that send it to Brazil 
Thank you by the way…
No!!! The sensor on the heated bed is tough as hell. The sensor inside the print head is very delicate!
ok, I got it! 
Yes. Seen it dozens of times on the forum. That was why I said that was the most likely problem 2 months ago.