[TLDR: What is the best way to troubleshoot an arduino that crashes 50% of the time on power up running a simple test script]
Hello! Hopefully this is the correct sub-forum 
I have a project that uses the Leonardo bootloader that has worked fine for months using a firmware that my friend downloaded (I can get more details as needed). The firmware had the infamous Leonardo 8 second delay with LED burst, so I decided to use Arduino's Burn Bootloader feature with an ISP. It seemed to work great, but now even with a test program that only turns on one LED, the hardware locks up 50% of the time on power up. When it does boot up correctly, it works as expected. I tried to re-burn the bootloader a few times with no change. I also reinstalled the newest Arduino IDE and re-burned the bootloader from that. Any troubleshooting advice would be greatly appreciated!