Computer's level always changes

I often play chess versus Lichess StockFish Computer and recently I have noticed that the Computer's level changes time by time. Sometimes the level five behaves as the level eight and another time it behaves as the level three. It is crazy. I also have faced with different bugs and one noticeable is when a game starts and I play for black side, white side doesn't move and I have to restart the game. Sometimes it looks like that you trying to prevent a DDos attack or I don't know, maybe you don't like when players play with the computer too often.