While using an ft232 usb-serial monitor between a pair of Pi2 systems 
an odd behavior was observed. 

An ssh connection to the first Pi2 opened a shell, in which
tip was invoked to monitor the serial console of the second
Pi2. A top session was left running continuously on the second
Pi2.

After some time the ssh connection dropped for several hours.
Upon re-establishing the ssh connection and re-starting the
tip session output from top was still being received, with
an apparently huge backlog of buffered output. Eventually
that cleared, but the top display alternated between about
six and ten lines, with all keyboard commands being ignored.

Using an existing ssh connection to the Pi2 running top
killall top
was used to end the top session, leaving a shell prompt
in the tip session. It turned out that keyboard input
to that shell prompt didn't echo, suggesting it was not
sent.

The ftdi adapter was reset by running 
usbconfig .... power_off followed by
...............power_on and restarting the tip session.
Normal operation resumed. 

Restarting top in the tip session returned normal behavior.

20250515