How to detect the external low-frequency vibration crystal work?When it doesn't work how to switch frequency crystals?

[juge90]

52832，SDK12.0.0

I met such a situation: In the use of JLink burning program or air upgrade, after the completion of the program card died in initialization low-frequency crystals.

"sd_softdevice_enable(p_clock_lf_cfg, softdevice_fault_handler);"