I think I might have shorted something by accident. I have just purchased the Elegoo Robot Car Kit v2.0. Putting things together was relatively easy. I also managed to run the first example, which basically turns on and off the servos indefinitely for short periods of time making the small robot drive in one direction forwards, then go backwards, spin a little to pick another direction and repeat.
The second thing I wanted to test was the IR remote control. For some reason the LED that is part of the small board where the IR diode is placed didn't blink at all whenever I was pressing a button on the remote control. The car also didn't move even the slightest.
So it was time to get the multimeter out and test what goes on. The problem is that the thing is very small and I accidentally rubbed one lead into the other while having current flowing. The result - everything shutdown...slowly.
Needless to say I got scared that the board (Elegoo's version of the Arduino UNO R3) died. However it seems that's not the case since upon turning it off (I tried both the USB as well as the batteries as a power source) the ON LED turned on and the other LED that is supposed to be blinking is blinking. The sensor board (it allows connecting IR, Bluetooth, the ultrasonic sensor etc. to the Arduino board) also has it's red LED turned on.
However using the same example program now my robot is not moving at all. Instead I can hear at least from on of the motors a clicking sound and also tiny vibration which (it seems) is caused by the motor where the sound comes from and is the result of it attempting to move the wheel attached to it.
I checked the power connector of the servo control board (an H-bridge for 4 servos - one per wheel; uses the L298N) and when I turn on the batteries I get approx. 8.2V which is what I'm expecting to get (two rechargeable Li-Ion batteries BRC 18650 4200mAh, 3.7V each - why I get the higher reading is beyond me). So it's not that the board doesn't get the power. Something else is causing the issue and because of my lack of knowledge I am stuck wondering what has happened.
PS: The IR tranceiver seems to work or at least the LED attached to it blinks now whenever I press a button on the remote control. XD
EDIT: Small update. Sometimes the servos do work. After the n-th time turning the thing on and off all of a sudden all the wheels started moving. But then they stopped again.