avrdude: verification error, first mismatch at byte 0x0042 0x14 != 0x08

Hi,

i've been trying to upload a sketch to my arduino Uno and avrdude give me an error every time

avrdude: verification error, first mismatch at byte 0x0042
0x14 != 0x08
avrdude: verification error; content mismatch
avrdude: verification error; content mismatch

i tried to upload the sketch on another uno board and its working fine no problem. Anyone knows why is it why avrdude is giving me this error ?

Thanks