Thanks for the report. I was able to reproduce the bug. I have an idea what may be causing it, but I'm not sure it will be easy to fix. I may try to address it someday, but it's not a priority for an immediate fix. While annoying, this bug is easy to work around. I've added a warning to the game's description. The game is also available here and here, and these versions are not affected by this bug (AFAIK).