Media 100 Suite v2.1.8 should be considered "beta" software for macOS High Sierra (version 10.13). If you are willing to try Media 100 Suite v2.1.8 with High Sierra, please report feedback on the Media 100 Facebook Group or at Creative COW.
When testing beta software, we strongly recommend setting up a test system, and not installing the software on a system you are counting on production.