m-x Keep Lines bug reproduction

[Moon at MIT-AI (David A. Moon)]

In the version of zwei on system 36.2, with microcode 683, on LISP Machine Eight:
(This happens in 37.1 also)

Type c-X ( FOO return BAR return BAZ return QUUX return c-100 c-x )
This will take absurdly long to execute, but that's another problem.
When it finishes, do m-< m-x Keep Lines return FOO return.  Looks like
it works, but hit m-> and notice that the top line on the screen says
"BAR"!  The rest of the lines say "FOO" as they should, though.
For extra fun, try hitting c-P or m-V at this point; it will blt the
screen a strange amount then get an error in redisplay.