Fix extension host loading (codesandbox#3165)

Author: CompuIves

packages/app/src/app/overmind/effects/vscode/index.ts

@@ -292,6 +292,8 @@ export class VSCodeEffect {
   public async changeSandbox(sandbox: Sandbox, setFs: (fs: SandboxFs) => void) {
     await this.initialized;
 
+    const isFirstLoad = !!this.modelsHandler;
+
     if (this.modelsHandler) {
       this.modelsHandler.dispose();
     }
@@ -311,10 +313,14 @@ export class VSCodeEffect {
 
     setFs(this.sandboxFsSync.create(sandbox));
 
-    this.editorApi.extensionService.stopExtensionHost();
-    this.sandboxFsSync.sync(() => {
-      this.editorApi.extensionService.startExtensionHost();
-    });
+    if (isFirstLoad) {
+      this.editorApi.extensionService.stopExtensionHost();
+      this.sandboxFsSync.sync(() => {
+        this.editorApi.extensionService.startExtensionHost();
+      });
+    } else {
+      this.sandboxFsSync.sync(() => {});
+    }
   }
 
   public async setModuleCode(module: Module) {