Saving a map with incorrect object paths errors and deletes the map.

[ninjanomnom]

There are probably also mapping var edits for vars that don't exist anymore. Where dream maker would ask for what you want the new paths to be, fastDMM instead doesn't have an issue until you want to save changes.

[ZeWaka]

What's worse, it also saves the map once it's been deleted, leaving you with an empty map.

Edit: Interestingly enough, this does not occur just because of path errors. It occurs on just some maps for me, and they all compile fine.