Hard fault from nrf_log_frontend_dequeue()

Hi,

I'm getting a hard fault that I really need some help to debug. My call stack is shown below and includes nrf_log_frontend_dequeue() as well as a custom service function which calls sd_ble_gatts_hvx().

I checked the CFSR upon the fault following this guide and the only error flag set is for the following:

"IACCVIOL - Indicates that an attempt to execute an instruction triggered an MPU or Execute Never (XN) fault."

This error occurs in two cases:

(1) immediately upon connection with the peripheral device if--and this is a sort of strange condition--if SAADC acquisition time is set to 1us or 5us (NRF_SAADC_ACQTIME_1US)

(2) rarely/sporadically if SAADC acquisition time is set to anything >5us

One connection is that my custom function ble_sws_meas_send is called by the SAADC callback. But the frequency of SAADC reads is set independently of acquisition time, so I don't know why this would have an effect. 

Thanks in advance!