If you’ve been experiencing issues trying to get your app to Apple in the past couple of days, you aren’t alone. We are hearing rumbles from around the Internet that Apple engineers might be fighting an issue surrounding bitcode (enabled or disabled) during app thinning. It’s something that I experienced myself over the past 24 hours.
The message most are receiving looks something like this: '...errors occurred in the app thinning process, and your app couldn’t be thinned. If your app contains bitcode, bitcode processing may have failed. Because of these errors, this build of your app will not be able to be submitted for review or placed on the App Store. For information that may help resolve this issue, see Tech Note 2432.”
App thinning according to Apple is tailoring app delivery to the capabilities of the user’s particular device, with minimal footprint. This optimization, called app thinning, lets you create apps that use the most device features, occupy minimum disk space, and accommodate future updates that can be applied by Apple. Faster downloads and more space for other apps and content provides a better user experience.
Hopefully they will have the issue resolved sooner than later but meanwhile here are a few resources to keep an eye on:
We'll keep you updated if we here anything further.