When attempting to launch a Fabric modded instance, users may encounter a crash with the error message Uncaught exception in thread 'main' java.lang.RuntimeException: error remapping game jars. This issue can be caused by an exclamation point (!) in the instance name.

Another issue involving special characters in instance names involves colons (:). When exporting a Modrinth modpack, you can get an empty file if the instance name has colons in it.

To resolve both of these issues, you must rename the folder to remove the exclamation point or colon. Ensure you have closed the launcher before renaming the folder, because you may encounter issues if you do it while the app is open.

In the future, this bug will be fixed in the Modrinth App itself by not allowing you to put these special characters there in the first place. For now, however, you will need to intervene manually to fix it.