Hello, it seems to be a hardware problem. I programmed a new Samsung chip as well as the old one and thanks to my trinocular stereomicroscope I soldered it clean but so far without success.
I have found that (the RT9018B Voltage Regulator) shows U807 on the capacitor C837 times 2.5V or 0.38V. The voltage regulator could be the problem. Could the Broadcom CPU be broken? I ordered the RT90188 Voltage Regulator but it will take a while, until it arrives.