At certain points in the code a call to a known good subroutine jumps into a .word disassembly and fails to execute

I've bypassed the timer for the TWR code and now have that running in an infinite loop just like the Decawave examples. I've also commented out the advertising start and do not appear to be going into the .word disassembly now. I'm going to focus now on getting the TWR up a nd running and then tackle getting the BTLE stack running with the TWR. I'll keep this open for now.

If the issue was indeed related to priorities, I suggest you check out the Using a Timer Expiry Function section in the k_timer documentation. By doing it as shown in the example snippet there, the task that is done inside the work handler can run even though the timer interrupt priority is higher than the task performed in the work handler. 

BR,
Edvin

If the issue was indeed related to priorities, I suggest you check out the Using a Timer Expiry Function section in the k_timer documentation. By doing it as shown in the example snippet there, the task that is done inside the work handler can run even though the timer interrupt priority is higher than the task performed in the work handler. 

BR,
Edvin