Actually, it's not a bug. In an OTB game, you must claim the draw after the position has repeated three times-if you silently sit there and your opponent does the same, it won't be drawn.
Once the position repeats for the third time, you can press the draw button, and it won't be a draw offer (your opponent won't be asked of his opinion)-the game will end in a draw instantly.
Do you notice that is not draw game when the moves repeat 3 times! That is the error in this site, which is (site) in fundament very good. I play game in draw situation, but after 3rd repeat, program is not stop game by draw. Of course, I lost in the end. :)