Netflix says I've watched episodes I haven't.

Say there is a show with 10 episodes. I will watch episodes 1, 2 & 3 and log off. Next time I go back, Netflix will show episodes 4, 5 & 6 watched too, even though I never watched them, and start me on episode 7.

This has been a problem for a while. Happens regardless of platform (laptop vs my tv). I'm the only person on my account.

Any idea what is going on?