If you can still DFU the flaky one, can you try this latest Factory Core-Firmware BIN?
https://github.com/spark/core-firmware/raw/spark_2/build/core-firmware.bin
Maybe you already have.. not sure 
I have gotten into a couple situations now where I had to completely erase the memory from 0x8005000 all the way up to get my core to respond again. This is where the core-firmware.bin goes, so if you are able to reprogram that with the link above, and it's still acting funny.. (orange flash) You might need new Keys: