Nrf52840 Custom Board Program Booting error

Hi, 

I"ve designed a custom board with the MDBT50Q module (part of the schematic below). When writing my program to Flash 0 and Ram Memory 2000 0000, the program won't load and will lock up, becoming unable to connect or program again. However, the board will suddenly boot up the program randomly after I power cycle (detach and reattach power) it enough times. When the board does boot up by chance after numerous power cycles, I can erase the program hence resetting the board. However, whenever I try to load a new piece of software into the board the exact same error happens (where it locks up and requires multiple power cycles until it becomes addressable again) 

I've tried using both the internal and an external oscillator. I've configured the sdk_config and am writing to Flash 0 and Ram memory 2000 0000 with no soft device. Moreover, I've ordered multiple custom boards + modules each giving the same error.

Does anyone know what might cause this type of error?