[raybbr]

I almost added solar wind to the list but honestly I can’t envision it having enough energy to shift the orbit of a satellite.

[Lucky Dog]

The effect is, in deed, typically very small. Nonetheless, it is present and the surface area exposed and length of time for exposure are factors.

Added to other potential factors it can have a cumulative influence especially in possible, synergistic combination with magnetic or gravity anomalies (e.g., small unobserved asteroid) and other unplanned events, e.g. propellent tank leak, etc.

The point was that there are a number of potential sources, either singly, or in combination, that can account for orbital drift.