Items that can't be fixed?

Please say it is not the audio not being heard in mimoCalls.

What are the items that “we can’t fix.”?
Last lines from the latest, 5.7.1b MimoLive Beta, ‘System Requirements’.
“mimoLive requires a Mac running macOS 10.11 or higher. We highly recommend using macOS 10.14 (Mojave) as there are some critical crashing bugs in previous macOS releases we can’t fix.”

Thanks for drawing my attention to this note. It should actually recommend 10.15 Catalina.

The bugs we can’t fix are things in macOS that don’t work and have been fixed by Apple in newer OS versions. Both 5.6.1 and 5.7b1 contain fixes for audio issues that also effect mimoCalls, so please give 5.7b1 a try.