Any idea how to check the G S and D with the cable installed? I tried searching for a schematic of the cable to no success.I have new theory on why the cmd resistor died. Try to change the cmd resistor in pico which is 47ohms into around 100ohms.
The cmd resistor (on the board) is a pullup resistor 4k7 to 1.8v. I am not sure, whether picofly send something to cmd line, which i assume it is. And i am not sure on what voltage the rp2040 send the signal, which i assume its 3.3v. So It could be that the current flows in the cmd line is too big for that cmd resistor (4k7) to handle, so pico burns it. The easy one is to increase the resistor on the pico to 100 ohms. Its still on the range of emmc specification, and also limiting the current. Might solve the mysterious cmd burns issue.
Test the D line of mosfet to GND, if its 12 Ohms then the D and S is soldered correctly. If is read 0-3 ohms, means the solder between 2 pads of the cap are short circuit. If its read huge resistance or open circuit then its means the soldered tin (D and/or S) is not touching the capacitor pad.
Check also the resistance D-G and S-G also S-GND. Just to make sure. D-G should be high resistance, S-G high resistance and S-GND 0-3 ohms.
There are 6 pin on the flex, The middle pin 3,4 is the G, the else you need to check yourself, i forgot.