avrdude: verification error; content mismatch on Adruino Uno R3

Hi, I've uploaded a sketch on the Arduino Uno R3 to flash an LED on pin 13, had a 20Ohm resistor in series with LED, the first upload worked, but every upload after that failed with the below error.

I've tried on multiple computers and operating systems, always get the same error even if I upload a blank sketch.

Could the bootloader be damaged, or does it look more like a faulty unit?

Arduino: 1.8.12 (Windows 10), Board: "Arduino Uno"

Sketch uses 444 bytes (1%) of program storage space. Maximum is 32256 bytes.
Global variables use 9 bytes (0%) of dynamic memory, leaving 2039 bytes for local variables. Maximum is 2048 bytes.
C:\Users\User\Downloads\arduino-1.8.12-windows\arduino-1.8.12\hardware\tools\avr/bin/avrdude -CC:\Users\User\Downloads\arduino-1.8.12-windows\arduino-1.8.12\hardware\tools\avr/etc/avrdude.conf -v -patmega328p -carduino -PCOM6 -b115200 -D -Uflash:w:C:\Users\User\AppData\Local\Temp\arduino_build_286903/sketch_feb24a.ino.hex:i 

avrdude: Version 6.3-20190619
         Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/
         Copyright (c) 2007-2014 Joerg Wunsch

         System wide configuration file is "C:\Users\User\Downloads\arduino-1.8.12-windows\arduino-1.8.12\hardware\tools\avr/etc/avrdude.conf"

         Using Port                    : COM6
         Using Programmer              : arduino
         Overriding Baud Rate          : 115200
         AVR Part                      : ATmega328P
         Chip Erase delay              : 9000 us
         PAGEL                         : PD7
         BS2                           : PC2
         RESET disposition             : dedicated
         RETRY pulse                   : SCK
         serial program mode           : yes
         parallel program mode         : yes
         Timeout                       : 200
         StabDelay                     : 100
         CmdexeDelay                   : 25
         SyncLoops                     : 32
         ByteDelay                     : 0
         PollIndex                     : 3
         PollValue                     : 0x53
         Memory Detail                 :

                                  Block Poll               Page                       Polled
           Memory Type Mode Delay Size  Indx Paged  Size   Size #Pages MinW  MaxW   ReadBack
           ----------- ---- ----- ----- ---- ------ ------ ---- ------ ----- ----- ---------
           eeprom        65    20     4    0 no       1024    4      0  3600  3600 0xff 0xff
           flash         65     6   128    0 yes     32768  128    256  4500  4500 0xff 0xff
           lfuse          0     0     0    0 no          1    0      0  4500  4500 0x00 0x00
           hfuse          0     0     0    0 no          1    0      0  4500  4500 0x00 0x00
           efuse          0     0     0    0 no          1    0      0  4500  4500 0x00 0x00
           lock           0     0     0    0 no          1    0      0  4500  4500 0x00 0x00
           calibration    0     0     0    0 no          1    0      0     0     0 0x00 0x00
           signature      0     0     0    0 no          3    0      0     0     0 0x00 0x00

         Programmer Type : Arduino
         Description     : Arduino
         Hardware Version: 3
         Firmware Version: 4.4
         Vtarget         : 0.3 V
         Varef           : 0.3 V
         Oscillator      : 28.800 kHz
         SCK period      : 3.3 us

avrdude: AVR device initialized and ready to accept instructions

Reading | ################################################## | 100% 0.00s

avrdude: Device signature = 0x1e950f (probably m328p)
avrdude: reading input file "C:\Users\User\AppData\Local\Temp\arduino_build_286903/sketch_feb24a.ino.hex"
avrdude: writing flash (444 bytes):

Writing | ################################################## | 100% 0.08s

avrdude: 444 bytes of flash written
avrdude: verifying flash memory against C:\Users\User\AppData\Local\Temp\arduino_build_286903/sketch_feb24a.ino.hex:
avrdude: load data flash data from input file C:\Users\User\AppData\Local\Temp\arduino_build_286903/sketch_feb24a.ino.hex:
avrdude: input file C:\Users\User\AppData\Local\Temp\arduino_build_286903/sketch_feb24a.ino.hex contains 444 bytes
avrdude: reading on-chip flash data:

Reading | ################################################## | 100% 0.06s

avrdude: verifying ...
avrdude: verification error, first mismatch at byte 0x010f
         0x80 != 0x90
avrdude: verification error; content mismatch

avrdude done.  Thank you.

Could the bootloader be damaged, or does it look more like a faulty unit?

Some people have fixed this problem by re-burning the bootloader. Use your other UNO and try it.

https://www.arduino.cc/en/tutorial/arduinoISP

Thank you for the reply!

I will try this!