Issue after migrating storage from local to S3

We migrated our storage from local storage to S3, and the S3 integration itself appears to be working correctly. Builds are successfully uploaded to S3, and newly created files in the bucket can also be accessed/used normally.

However, all newly deployed Functions and Sites are failing to load and return:

Timed out waiting for runtime.
Error Code: 400

This appears to be specifically affecting the runtime initialization/execution of newly deployed Functions and Sites, rather than S3 file upload or file access itself.