Help needed!

I drive a 97 VW Golf GTi 8 valve – great motor & having lots of fun driving it! But (there is always a but!) I have one problem the digital odometer. There are two of them, the one in the rev counter works fine & I have no problems with it at all! The one in the speedo counter is the problem, it seems to read as it should one/two days then goes on the blink for a couple of weeks & then sorts itself out again for another couple of days then back on the blink!

Any help or advice will be much appreciated!

Cheers,

Murt