Onboarding Friction for EU-based Trading Entities with US-based Brokers

We're an EU-based prop firm consistently facing significant friction during the KYB process with US-based prime brokers, even after providing comprehensive documentation and having clean regulatory records. It often feels like a black box, with repeated requests for the same information, vague reasons for delays, and a general lack of transparency in the estimated onboarding timeline. Has anyone else encountered this persistent bottleneck, particularly around demonstrating beneficial ownership or intricate corporate structures? Are there specific types of documentation or pre-emptive measures you've found effective in streamlining this process, or is it just the cost of doing business across these jurisdictions?