2021-007 Security Update Catalina - Pioneer DJ Rekordbox

Never a good idea to install Apple updates just after they have been released, too often these days they can

introduce bugs of their own, as you have found out.

If this is deemed an Apple issue they may release another update or supplemental update in the next few days/ weeks.

Have you contacted the developers of the software like Rekordbox to see if they are aware of the issue and if they may be planning an update for their software.

Apple is not here to read your post, if you want to let Apple know the problem you are facing then you can let them know here,

https://www.apple.com/feedback/macos.html

If you know lots of others that have the same problem then you can pass the link on to them as the more people that make Apple aware of an issue the more likely they may do something.

Before you installed this Security Update did you make a full backup of your mac, if so you could restore your mac to that backup before the update to regain functionality.