I have the occasional issue where connecting VDD to VTG either on P20 or shorting SB24 will cause the nRF9160 DK to brown out. This happens when an external device to be programmed is connected. The issue appears to be related to the XC9236 itself. I took a quick capture of what's happening. See below:
My guess is there is something internal to the XC9236 which is turning off the output. First guess is the UVLO but since the drop is about 700mV. It never recovers though.. My best guess is the culprit is D10.
I'm using PCA10090 v1.1.0.
