zero, you are correct that the exact position and velocity (more correctly momentum) cannot be SIMILTANEOUSLY determined precisely for an individual electron, even theoretically. This is not because of interaction with other particles but because in their essential existence an electron simply doesn’t have a definite existing simultaneous position and momentum! It is a matter of probabilities.
I don’t claim to really understand this Heisenberg principle. Physicists are apparently unable to grasp it either though they can certainly describe and use it.