* What can I do to debug early boot problems?You can at first try enabling debug output. (make menuconfig --> Build Setup --> Debug Options --> Enable Debug Features). You should have some information regarding what's going on. Another option is to enable DEBUG_SYMBOLS and debug the startup code.
A breakpoint on up_assert should catch any early crashes as you describe. There is a cool debug tip here if you hit the breakpoint: *https://nuttx.events/wp-content/uploads/2019/11/DSidrane_nx2019.pdf*
