qemu fails to scroll screen on ^Vidmem output

Pascal uses ^Vidmem for B800 console output. The terminal does not oblige the Pascal OS code to scroll the output. Virtualbox emulation works, so this must be a qemu bug. Using QEMU in KVM mode as Ubuntu LTS.

Source line to trip bug(in theory pushes VideoMem up one line):

procedure Scroll;
//this is whats causing crashes. FIXME:Virtualbox not affected.QEMU BUG?
begin
  if scrolldisabled then exit;
      if (CursorPosY >= 24) then begin  //in case called before end of screen
    blank:= $20 or (TextAttr shl 8);
    Move((VidMem+(2*80))^,VidMem^,24*(2*80));
    // Empty last line
    FillWord((VidMem+(24*2*80))^,80,Blank);
    CursorPosX:=1;
    CursorPosY:=23;
    update_cursor;
  end;
end;