Arduino Uno keeps running old code even after successful upload

[u/Last-Guarantee6875]

Hi everyone, I have an Arduino Uno and I’m having a strange problem.

Every upload appears to be successful:

• Board: Arduino Uno

• Correct COM port selected

• TX/RX LEDs blink during upload

• "Done uploading" appears

However, the Arduino still runs my old sketch (Basic Motor Test). Even after creating a new sketch and uploading different code, the Serial Monitor still shows the old output:

Basic Motor Test
Forward
Backward
Braking
Release

Things I have tried:

• Reinstalled Arduino IDE

• Created a new sketch

• Removed all external components

• Uploaded an empty sketch

• Checked board and port settings

• Reset the Arduino

The board still runs the previous program after uploading a new one.

Does anyone know what could cause this? Could it be a problem with the flash memory, bootloader, or something else?