Bootloader resets after switching to DFU

Question

Hi, 
 I have a huge issue with NRF52832 and DFU on custom board. I have a custom characteristic in my application to switch to DFU after proper PIN typing. Then I call this function: 
 uint32_t switch_to_dfu() {

 uint32_t err_code;
 err_code = sd_power_gpregret_clr(0, 0xffffffff);
 VERIFY_SUCCESS(err_code);

 err_code = sd_power_gpregret_set(0, BOOTLOADER_DFU_START);
 VERIFY_SUCCESS(err_code);

 err_code = sd_power_gpregret_set(1, BOOTLOADER_DFU_SKIP_CRC);
 VERIFY_SUCCESS(err_code);

 nrf_pwr_mgmt_shutdown(NRF_PWR_MGMT_SHUTDOWN_GOTO_DFU);
 return 0;
} 
 After that device resets to bootloader and there is such a code: 
 // Protect MBR and bootloader code from being overwritten.
 uint32_t ret_val = nrf_bootloader_flash_protect(0, MBR_SIZE, false);
 APP_ERROR_CHECK(ret_val);
 ret_val = nrf_bootloader_flash_protect(BOOTLOADER_START_ADDR, BOOTLOADER_SIZE, false);
 APP_ERROR_CHECK(ret_val);

 (void) NRF_LOG_INIT(app_timer_cnt_get);
 NRF_LOG_DEFAULT_BACKENDS_INIT();

 NRF_LOG_INFO("Inside main");

 ret_val = nrf_bootloader_init(dfu_observer);
 APP_ERROR_CHECK(ret_val);

 // Either there was no DFU functionality enabled in this project or the DFU module detected
 // no ongoing DFU operation and found a valid main application.
 // Boot the main application.
 nrf_bootloader_app_start();

 // Should never be reached.
 NRF_LOG_INFO("After main"); 
 Unfortunately bootloader stops in nrf_dfu_req_handler_init and device resets and after that go to application. 
 That all happen when I erase whole code using nrfjprog/nrfconnect and then flash it bl_sd_app_with_settings.hex. When I use OpenOCD 0.10.0 trying to debug and use mo reset halt command problem disappear (but problem isn't in optimization flag). Everything works fine. 
 Any thoughts?