Error: godot failed to unload assemblies

What's Causing This Error

The error "godot failed to unload assemblies" typically occurs in the context of Godot Engine when working with C# scripts or modules. The engine uses Mono to handle C# scripting, and as such, needs to load and unload assemblies which contain the compiled code of your scripts. Here are some common causes for this error:

1. Locked Assemblies: If something is using the assemblies outside of Godot (like a background process or another instance of the editor), they cannot be unloaded because they are locked.
2. References Not Cleared: Objects from the assembly may still be referenced in your code or by the Godot runtime, preventing the assembly from being unloaded.
3. IDE Locking Files: Sometimes Integrated Development Environments (IDEs) like Visual Studio or Rider might lock files while debugging or due to certain settings.
4. File Permissions: The user running Godot might not have the correct permissions to modify or delete the assembly files.
5. Bugs in Godot: There could be a bug within the version of Godot you are using, especially if it is a beta or an unstable release.

Solution - Here's How To Resolve It

Addressing the issue requires checking several potential problem areas and applying the following solutions:

1. Close Other Instances: Ensure that there are no other instances of Godot or any text editors that might be accessing the same project files open.
2. Stop Background Processes: Close or kill any background processes that might be using the assemblies.
3. Check References: Make sure that all references to objects that live in your assemblies are properly disposed of and set to null where appropriate before unloading.
4. Restart IDE: If using an IDE, close and reopen it to release any file locks it may have created.
5. Run as Administrator: Run Godot as an administrator to ensure it has permission to modify the files it needs to.
6. Update Godot: If you suspect a bug in the engine itself, check for updates to Godot or report the issue to the Godot GitHub repository.
7. Manually Delete Assemblies: As a last resort, manually delete the .mono folder in your project directory (after backing up your project). This forces Godot to recreate the assemblies from scratch.

Before trying these solutions, make sure to backup your project to prevent any data loss.