I don’t think a single voting machine has been caught built to cheat toward or against any candidate or party as such.
Voting machines are often far more complex than they need to be, the more hooks to hang monkey wrenches on. They sometimes do not enforce programming rules that ensure data consistency whenever the same candidate is referred to in multiple places.
We use the optical scanners in my little town and we don’t seem to have any problems. They’re trying to push touch screen computers on us by having one available but it sits mostly unused as people wait for a booth to fill out ballots the old fashioned way.