I use non contact voltage tester function of Uni-t ut210e for detecting main wires under/in walls. It worked pretty well until yesterday.
The wall is made of bricks/mortar and some metal profiles (as I experienced today when drilling holes for wall shelf). There is 0 voltage between that metal profile and the ground.
Also, there is a wall socket 20 cm from the bottom of the wall. Mains voltage is 230 V.
What could be the cause of NCV meter beeping over almost entire wall?