To attempt a repair you just need to do the following:
- Open your Black Desert Online Launcher.
- Click the cogwheel located on the top right corner of the Launcher window.
- Next to "Repair Mode", click the "Click to start" button, and select "Yes" to initiate a file repair.
Please note that, it may look like the launcher is (re)downloading a massive amount of data but it will actually only download damaged files after checking the whole installation.
Should you continue to have problems, please send in a ticket below.