K8400, Temperature is slowly dropping down to room temp

Hi all!
I have problem with my K8400 regarding temperature dropping down to room temperature!
The first 2 months the printer worked very good.
After that, the temperature starts to drop from 200°C very slowly. Printer continues printing with known result as temp falls.
What I have done:
I checked and noticed that the red LED turns off after a few minutes.
I have checked all cables and cant find any problem with that. Unscrewed cables and screwed them back again
I bought a new NTC and also a new heater element.
Still the same.
I checked so that the NTC was perfectly mounted.
Still the same.
I removed again NTC and heater and added thermal compound to be sure of good thermal connection.
When I started printer I saw that temp was going up fast to about 190°.
Still the same.
Sorry to say, now I have run out of options…
Can it be something in the PCB board?
I would be very happy for some help here!

Regards
BoJ

Hi

Check on the motherboard if the heater connector is properly seated.
Pictures are always helpful.

Best Regards,
VEL337