diff --git a/code/lib/core-server/src/utils/StoryIndexGenerator.ts b/code/lib/core-server/src/utils/StoryIndexGenerator.ts
index 39e9817d77f6..6d8817147f0f 100644
--- a/code/lib/core-server/src/utils/StoryIndexGenerator.ts
+++ b/code/lib/core-server/src/utils/StoryIndexGenerator.ts
@@ -113,7 +113,7 @@ export class StoryIndexGenerator {
 
   async initialize() {
     // Find all matching paths for each specifier
-    await Promise.all(
+    const specifiersAndCaches = await Promise.all(
       this.specifiers.map(async (specifier) => {
         const pathToSubIndex = {} as SpecifierStoriesCache;
 
@@ -132,10 +132,16 @@ export class StoryIndexGenerator {
           pathToSubIndex[absolutePath] = false;
         });
 
-        this.specifierToCache.set(specifier, pathToSubIndex);
+        return [specifier, pathToSubIndex] as const;
       })
     );
 
+    // We do this in a second step to avoid timing issues with the Promise.all above -- to ensure
+    // the keys in the `specifierToCache` object are consistent with the order of specifiers.
+    specifiersAndCaches.forEach(([specifier, cache]) =>
+      this.specifierToCache.set(specifier, cache)
+    );
+
     // Extract stories for each file
     await this.ensureExtracted();
   }
diff --git a/scripts/tasks/sandbox-parts.ts b/scripts/tasks/sandbox-parts.ts
index 0f826a81343e..967b826518e9 100644
--- a/scripts/tasks/sandbox-parts.ts
+++ b/scripts/tasks/sandbox-parts.ts
@@ -432,9 +432,9 @@ export const addStories: Task['run'] = async (
 
   if (isCoreRenderer) {
     const existingStories = await filterExistsInCodeDir(addonDirs, join('template', 'stories'));
-    await Promise.all(
-      existingStories.map(async (packageDir) => linkPackageStories(packageDir, { mainConfig, cwd }))
-    );
+    for (const packageDir of existingStories) {
+      await linkPackageStories(packageDir, { mainConfig, cwd });
+    }
 
     // Add some extra settings (see above for what these do)
     if (template.expected.builder === '@storybook/builder-webpack5') {