using tip on machine that has COMCONSOLE set to serial

This may be a dumb question, but I have 
a situation where machine A and B both have
enabled serial console. I'm ssh'ing into A to
try and debug a problem on B. I'm trying to
use tip, but am getting interference from the 
fact that A also has a serial console.

If i disable the getty, its a bit better.

Is there a way to make this work reliably, or
am I SOL?

--don