I remember in the 90s, they had just refurbished Red Hill, and the broncos were going pretty ordinary, Bennet said to them domething like "if you play like park footballers, then you don't deserve superstar facilities", and had them outside running. I think it was around the time they had $1500 for a win and 50 for a loss.
The thing was they were winning, but winning "dirty" if you know what I mean, with plenty of mistakes.
Right now, this side isn't winning and in situations like these, when morale is low, he'd usually get something that bonded the team happening. I think they need to start working for each other, and that starts with knowing each other and communicating. I'd schedule a team night out (only the team, doing something they need to work together with but completely unrelated to football: mayybesailing, or rockclimbing, or orienteering. It just needs to be fun, physical, but most importantly makes them talk and work together.
Having players dwell on their errors won't help right now, nor an extra drill session. Build some team cohesion, implement a simple but effective game plan, and drive the basics for now. Later, you can bring in more complex plays, but only when the team is effective using simple ones.
These things should have happened in the preseason (maybe they did) but for whatever reason there is a lack of "togetherness" in the way they play, particularly in defence.