I would use the Web device doctor firmware which can produce a log of where the device is failing.
However, the web-based log may not be sufficient in your case because the web-based log is delayed compared to the normal USB serial log. You may need to use the Particle CLI particle serial monitor command or other serial terminal instead.
It's also most likely power-related, so if you have a 2A micro USB tablet charger you might want to try that, but of course you won't be able to get log that way, but it's a good data point.