unintended internal discharge on STUSB4500?

[BonyFingers]

Hi I have a design with the STUSB4500 per the attached schematic snippet and programmed per the attached memory map.  This circuit is on a tiny board inside the plug end of a captured USB cable. The PDO's are programmed to default to 20V @ 3A.

The application is for a one-time use product (used for about 1 hour) and normally this works well.  However about 1% of the time the cable assembly appears to perform the following:
   1) properly negotiate 20V@3A (as seen on a cc line sniffer)
   2) shortly after 20V is applied by the DFP, enough current is drawn to bring down the power supply.
   3) power supply remains off until the cable is unplugged, then the cycle starts over when re-plugged in.
We can continue un-plugging, then plugging-in the cord (nothing else attached to the other end of the cable).  Sometimes we can do this twice, and other times 50 cycles until it just starts working.  Once it decides to work, it works without fail forever.  Is there something wrong with the circuit design that can be causing this intermittent failure?

[NBALL]

Hello

Sorry for the late feedback.
stusb4500 does not draw 3A, even in discharge phase: seems something is damaged on the failed PCB.

BTW are you sure that 20V falls because of overcurrent ? It can be that stusb4500 detects HW fault and removes its CC pin to go into 'errorrecovery'. This state emulates a cable removal. 
BTW I've checked the attached schematic and it is not correct: R6 shall be removed. Rd is inside stusb4500 and having additional resistor in parallel might affect behavior.
I also strongly suggest to have no more than 10k on R3.
SDA and SCL can be directly grounded. (Please refer to figure9 of our datasheet)
CC2 & CC2DB shall be connected together and grounded.

When system fails, it would be great to have oscilloscope capture of CC and VBUS pins

Best regards

Nathalie

Best regards

Nathalie