RPI2 drops _some_ ssh connection

[bob prohaska]

I've an RPI2 running 11.3-STABLE FreeBSD 11.3-STABLE #0 r351178
which seems to be dropping one of several active ssh connections.

With four connections active from terminal windows on a Pi3 running
raspbian, the one used to monitor a cu session keeps dropping every
half-hour or so. All the other connections, running ordinary user
processes like top or compiling a port, seem to stay up and running.

There has been a tendency for -current to do this on a Pi3, but 
11-stable didn't until the latest upgrade a few days ago. 

It doesn't look like a network problem, since all four sessions
are over the same wifi and wired links. Could there be some odd
interaction between cu and ssh?

Thanks for reading, and any thoughts....

bob prohaska