Hi,
MacMini running I7 was not reachable via VNC (but it was pingable); I7 Client from iMac could not connect, only after few retries.
I succeeded to connect to MacMini and had a look at Console.app and found a crash log for the IndigoPluginHost (see attachment, I added the extension ".log" because ".diag" was not accepted).
I do not know if IndigoPluginHost crashed because macOS had a problem or the other way around.
When I succeeded to connect to Indigo via Client on iMac I saw the plugin list totally empty.
Attached also the latest log file from Indigo (zipped and extension renamed to ".log").
Thanks
Marco