macOS 10.13 High Sierra is currently in BETA, and therefore is not supported in Serato DJ. We aim to complete testing and confirm compatibility as close to the public release as possible.
We are grateful for any feedback or issues that you may encounter using the BETA, and encourage you to open a ticket to report them, here. If you choose to use the macOS BETA with Serato DJ, you do so at your own risk.
Please be aware that to resolve issues you may need to roll-back to a supported macOS operating system.