What's going on here is that system messages (i.e. the syslog) is also getting spammed onto that terminal, so you're getting junk. That's not output from your command, just garbage spewed by something else. If you clear it with CTRL+L, it'll go away.
(This is a really annoying bug, IMO.)
I've tried doing CTRL+ALT+(other function keys) to get a different virtual terminal, if there's one enabled and that sometimes helps.
