Source HEAD:
Key: public/app.js
Content-Type: application/javascript
Cache-Control: public,max-age=31536000,immutable
ETag: "abc123"

Destination HEAD after migration:
Key: public/app.js
Content-Type: application/octet-stream
Cache-Control: <missing>
ETag: "abc123"

Users report browsers downloading the JS file instead of executing it.
