I'm using SDK nRF5_SDK_15.0.0_a53641a, and I was able to trigger the hard fault handler from within the Nordic NFC library. Nothing was running. The microcontroller was asleep when the NFCT interrupt fired.
Here's the call stack:
Here's the Disassembly of where it crashed:
Unfortunately, I disconnected the debugger and reset the device before I was able to grab the CPU registers. I'm not quite sure what I did to cause this, either. I was "abusing" the NFC by doing lots and lots of reads with an Android phone. If I manage to crash it again, I'll be sure to get more information.