I go the same thing, there was only one option before our second part of the live broadcast I needed to force stop Mimolive and restart the streams… I could not use save or save as or anything… very strange.
This phenomenon may be caused by backup software in general. Make sure that Time Machine and/or other backup solutions do not run while using mimoLive. Most of the backup solutions do change the access rights while the backup procedure. This should avoid changes while backup procedure. Well. A mimoLive document is changing all the time. (During transitions, for e.g.)
By the way: mimoLive needs very fast drives for I/O procedures. A network storage may not be fast enough. Especially when iCloud updates all the time all changes.