Officiating in an NBA game is not only very demanding, but a stressful job that requires carefully thought decision making, stamina, and the ability to maintain composure in close knit situations.
NBA officials must also be able to manage player interactions and understand the league’s rules and guidelines like the back of their hand.
Referees are human, and there is no such thing as a perfect human. There are no stopping mistakes from their end, especially with all the pressure they face in every game. Players, coaches and fans have always claimed that calls have been getting worse, “it’s been getting worse with each year.” But maybe it’s time to see it from their perspective.
NBA referees can be fined for making bad calls during games. The amount of money of each fine depends on the severity of the call, and larger fines being caused for more “outrageous” errors. But sometimes, referees can also be suspended for a game or even multiple games if their bad call is a cause to significantly impact the outcome of a game, playoff game or championship. In some cases, referees can even be fired..

Referees usually are held accountable for their actions and mistakes. The NBA has a process to review all referees and their decisions, and issue fines or suspensions as appropriate.
Take note that this “process” is not always clear and that the league doesn’t always act, and this could be since the NBA has to overview many other things not related to referring. Even when officials make obvious errors, there is a chance that the NBA might not take action, and this will lead to more referee mistakes since they will get used to not being punished. This lack of accountability is frustrating for fans, players and coaches.

This is why NBA referees are reviewed regularly, and this is to ensure that they stick to the league’s officiating standards. There are many different ways that officials can be reviewed, things like film study, this is to have a clear picture of what they did wrong, without being in a stressful situation, themselves. Another way of getting feedback, is feedback from players and coaches, along with data analysis. Data analysis for referees can be used as an overview from their last officiating game, and this includes videos with bookmarks of their certain plays to see if the call is right, or if there is any improvement they can make.
One of the most important methods of evaluating officials is a video review. This allows the league to see how well an official is calling games and identify any areas where the ref/referees need improvement.

Referees are also evaluated on the feedback from players and coaches. This can help the league see how well an official is communicating and making fair and consistent calls.

There is much more to being an NBA referee, but the stress and pressure factors may always be the same, or worse. It is important to respect the NBA referees for they are human, and make mistakes too.