In the 18+ hours I’ve played, I only had one enemy takedown mission where the number didn’t go down as I killed enemies. Other than that, I’ve never experienced any bugs in this game.
But I’ve played exclusively solo campaign mode, so maybe there’s something there. I did try to go online last night and it just errored out, so maybe multiplayer/online mode is buggy.
If you like, the developer displays his phone number on screen every time you die. You could try to reach out to him and let him know his game is broken. If he’s still engaged with the game, he might look into it.