BitBucket: https://bitbucket.org/namida42/neolemmixplayer/issues/25/scroll-position-reverts-to-levels-screen
1. Make sure you are zoomed into the level.
2. Scroll to a part of the level that is not the screen start (i.e. the portion of the level that you initially see when opening the level in the editor, and also opening the level in the NeoLemmix player).
3. Move/edit anything in that area.
4. Then press undo. In addition to the undoing, you are automatically scrolled back to the screen start portion. This can be really annoying when making large levels.
Fixed for the next update.