Obscure Vi bug?

[fredch at starlite.hf.intel.com]

Has anyone else experienced this?  I have AT&T/Intel Unix V/386 on my box:

Take a 50 line file (not sure if 50-line specific, but that's where I found it).
Go to 2 lines below the bottom line using the G command.  For example, under
TERM=xterm, go to line 25; under TERM=AT386 or TERM=vtpc, go to line 26.
Then type ^B.  It will beep.  Then, type j.  Suddenly the current line will
be copied onto line 1, and your file just got modified.
-- 
Fred Christiansen, Intel, JF1-67   503-696-4214 |  fredch at starlite.hf.intel.com
5200 NE Elam Young Prkwy, Hillsboro, OR  97124  | uunet!intelhf!starlite!fredch
Investment Advice: No investments of your time will produce as enduring results
    as time spent building character in your children.
----------
Fred Christiansen, Intel, JF1-67   503-696-4214 |  fredch at starlite.hf.intel.com
5200 NE Elam Young Prkwy, Hillsboro, OR  97124  | uunet!intelhf!starlite!fredch
Investment Advice: No investments of your time will produce as enduring results
    as time spent building character in your children.