Weird “Locking “ happening?

So I’m 1 year post surgery and due to some complications my recovery has been prolonged.

Recently I starter working out more and my knee has been feeling really good, but during my last workout something weird happened.

After some squats (with pilates ball against my back) when I went to straighten my leg somehow my knee locked and it was painful. After some time I managed to straighten it and something inside clicked- unlocked. I continued the workout and it happened a couple more times.

Now Im sick for a couple of days and been mostly laying down and the same thing happened when I tried to straighten the leg.

Has anyone had the same thing happen to them?