I have had multiple instances of the photon corrupting its flash when operating at low voltage.
This is a solar powered project that uses a small solar cell and lipo battery. I am using the low power sleep mode where the photon wakes every 30 minutes and reports data.
The photon will inevitably fail into a setup mode with a fast blue flash. The photon can be connected to and you can attempt to reset the wifi credintials but it will not connect to the cloud.
The fix was this:
Use the command line, plug in, put into DFU mode and run the following commands in this order.
particle keys doctor YOUR_DEVICE_ID_GOES_HERE
particle keys server
particle flash --usb tinker
Then re-flash your program