2000 Audi A6 - Cruise broken

My cruise control stopped holding the speed to the correct setting approximately a year or so ago. I have 155,000 miles on it. I set the cruise to lets say 70 mph, and every mile or so it’ll drop a mile or so, so after let’s say 5 miles of driving the speed is now 65 mph. Any ideas what could cause this ? Thank you for your help !

So I take it nobody has any ideas ?

9 months later . Good Greif , why have you not had it repaired?

Since cruise control system designs are very vehicle specific, my suggestion would be to pay a visit to an Audi dealer for a repair.

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I was thinking maybe an issue with a switch on the brake pedal or clutch pedal if the car has a manual.
If a manual an out of adjustment or worn clutch could cause this. A switch could be checked with an ohmmeter.

I can’t speak for certainty with this model but many cars have a rubber pad on the steel tab fitted to a clutch or brake pedal. Over time the somewhat pointy end of the switch plunger will cause a depression in the rubber pad as the aged rubber does not revert back to its original shape. Odds are the rubber pad is not available so one has to go in and improvise a bit.

Another possibility is a vacuum leak. This could be checked with a vacuum gauge or a smoke machine.
I realize the smoke machine may be a bit pricey for a DIYer but a vacuum gauge is cheap. The gauge will tell you if there is a leak. The smoke machine will show you where it is located at.
I’m not saying go this far but many years ago after pricing a smoke machine I decided to make one myself and it works just fine.