Yes, we have seen this lately as well.When you edit a file in the queue, it gets saved in the same directory the original file was in. If your original file was an STL, the edited version will get saved as an AMF instead. If your file was already an AMF, it simply gets overwritten.Unfortunately, right now MatterControl suppresses any errors encountered when saving files. If, for instance, you do not have permission to write to that directory, or there is no space left on the drive, then MatterControl will continue as if nothing went wrong and won't inform you of the issue. This is something we are investigating and will hopefully have fixed in the next version.