In NeoLemmix editor 12.0:
1) If you set a 'Lemming' limit for an exit, that requirement will be reset to 0 when you use undo/ctrl+z at any point after that. This occurs even if you freshly load a level that already had these requirements set, then use undo. If there's multiple exits, all of them are reset.
2) If you type a non-zero value for 'Lemming' on an exit, then click on a different object with a numerical input box (such as water or one-way walls), the following two errors occur:
(https://www.dropbox.com/s/ds83hd7a6upey2e/1.PNG?dl=1)
(https://www.dropbox.com/s/svn31o3f6aib3em/2.png?dl=1)