Submit a new bug on SourceForge by giving as much information as you can. Be sure to include the steps necessary to reproduce the problem and any files needed. Include the Fable version found on the Help menu.
Messages in the log are likely useful and should be included. The log is named Fable.log and should be found in your workspace directory. If you are unsure of what that directory is, you can determine it via Help | About Fable | Configuration Details. Look for user.dir.
Please give enough information and instructions so the problem can be reproduced by the developers. If the developers cannot reproduce the problem, it is unlikely it will be fixed.
This is the link for submitting a bug.
https://sourceforge.net/projects/fable/
Go to Develop then Tracker.