Crash enabling softdevice on Fanstel USB840F (based on nrf52840)

All examples included in nrf52SDK 15.2.0 when running on Fanstel USB840F which has a nrf52840 chip, using Segger Embedded Studio and one of PCA10056 or PCA10059.

Using nrf52DK with TagConnect cable attached to USB840F, I managed to debug the code and found the code crashes when calling:

ret_code = sd_softdevice_enable(&clock_lf_cfg, app_error_fault_handler);

included in "nrf_sdh.c" at line 214.

I report here the source for covenience:

 // Notify observers about starting SoftDevice enable process.
    sdh_state_observer_notify(NRF_SDH_EVT_STATE_ENABLE_PREPARE);

    nrf_clock_lf_cfg_t const clock_lf_cfg =
    {
        .source       = NRF_SDH_CLOCK_LF_SRC,
        .rc_ctiv      = NRF_SDH_CLOCK_LF_RC_CTIV,
        .rc_temp_ctiv = NRF_SDH_CLOCK_LF_RC_TEMP_CTIV,
        .accuracy     = NRF_SDH_CLOCK_LF_ACCURACY
    };

    CRITICAL_REGION_ENTER();
#ifdef ANT_LICENSE_KEY
    ret_code = sd_softdevice_enable(&clock_lf_cfg, app_error_fault_handler, ANT_LICENSE_KEY);
#else
    ret_code = sd_softdevice_enable(&clock_lf_cfg, app_error_fault_handler);
#endif
    m_nrf_sdh_enabled = (ret_code == NRF_SUCCESS);
    CRITICAL_REGION_EXIT();

    if (ret_code != NRF_SUCCESS)
    {
        return ret_code;
    }


    m_nrf_sdh_continue  = false;
    m_nrf_sdh_suspended = false;

What could be the issue?

Running the same examples on nrf52840 Dongle and nrf52840DK works well

Thanks in advance!