It looks the power source 5V_out has some problem and it may be caused by a broken diode on VBUS_TC to VCC_IN path. Can you measure if the 5V_OUT on the board is steady 5V?
My recommendation is to request your purchase channel to replace a new DVK.
These are my observations after measuring voltage through various test point on the Board:
(Note all these observations are taken after replacing the diode D6 with D7 as you said: "may be caused by a broken diode on VBUS_TC to VCC_IN path". Hence as both D6 and D7 diodes are identical, moreover, D7 diode was not in use as Vin is not being the power source.)
- 5V_OUT (VCC.5V) : The voltage on across this point is stable , but keeps in decreasing with subsequent measurements and the lowest value was 1.66 V .
- P6_VDD : The voltage across this point is fluctuating between 1.34 v - 1.28 v.
- J8 : The voltage on this pin is also fluctuating.
- The LED 4 is blinking with it's brightness going low up to a point where it is barely noticeable now.
- Even after replacing the with D7 diode it is still heating up.
- Blink program which I had already flashed before this issue occurred , is working fine when the the power is connected through J28 and the LED 4 is glowing at it's normal intensity. !
- This is a video link to it : https://youtu.be/GzDur6uSIfk
What about the level on VBUS_TC and VCC_IN?
Just from your observations, there are possible causes, one is broken diode, another one is broken 5V buck-boost convert. The 3v3 regulator is in good condition.