DFU serial failed

Hi guys,

i'm using DFU over serial and i get the error 4 in NRF_DRV_UART_EVT_ERROR.

This was not happening before and suddenly started.

<debug> nrf_dfu_flash: nrf_fstorage_write(addr=0x00040300, len=0x100 bytes), queue usage: 1
<info> dfu_req_handling: Storing 256 bytes at: 0x00040300
<debug> nrf_dfu_flash: Flash write success: addr=0x00040300, pending 0
<debug> nrf_dfu_flash: nrf_fstorage_write(addr=0x00040400, len=0x100 bytes), queue usage: 1
<info> dfu_req_handling: Storing 256 bytes at: 0x00040400
<debug> nrf_dfu_flash: Flash write success: addr=0x00040400, pending 0
<debug> nrf_dfu_flash: nrf_fstorage_write(addr=0x00040500, len=0x100 bytes), queue usage: 1
<info> dfu_req_handling: Storing 256 bytes at: 0x00040500
<debug> nrf_dfu_flash: Flash write success: addr=0x00040500, pending 0
<error> app: Received an error: 0x00000004
<info> app: Inside main

What could be the issue?

SDK: 14.1

board: nrf52832