Even GPS satellites aren’t in precise orbits. Their paths are perturbed by gravitational effects (the Sun, moon and mass anomalies of Earth itself) as well as atmospheric drag. Their positions are monitored on every orbit and adjustments are made to the ephemeris (which are loaded into all GPS receivers). In addition, thrusters are used to correct larger drifts from idea position.
Yes, there are perturbations and imperfections that are corrected for in the calculations. I considered this as TMI in replying to a person who was unsure about the types of satellites and their orbits.
Garde la Foi, mes amis! Nous nous sommes les sauveurs de la République! Maintenant et Toujours!
(Keep the Faith, my friends! We are the saviors of the Republic! Now and Forever!)
LonePalm, le Républicain du verre cassé (The Broken Glass Republican)