Now my Yappari has worked for more than 30 minutes (almost 2 hours actually).

But I have not 'spoken' to anyone except those I have communicated with since getting updated Yappari.

This leads me to conclude that the disconnections I was getting were 'soft-bans' for communicating with numbers I haven't synchronized ...

I'll put in a bug report on Github for synchronization issues. Just strange that I might be the only one whose Yappari crashes towards the end of Sync.