Does anyone have issues with customs when shipping from Europe to the US?

I’m experiencing significant issues with customs at FedEx Indianapolis. I ship all my packages from Romania to various Amazon FBA addresses using FedEx. Most of my shipments clear customs smoothly when they go through Memphis, but when they pass through Indianapolis, about half of my boxes get returned.

Some packages do clear customs, but many don’t. There’s no feedback or information provided, nothing at all. The packages arrive and are returned the very next day without even being inspected!

All the documentation is correct, and shipments with identical contents and paperwork clear customs elsewhere without any problems. Is anyone else encountering similar issues?