Hi. I’m experiencing a very unusual issue with a custom domain on Vercel and I’d like to know if anyone has seen something similar before. Domains Custom domain: https://samo-delo.ru Vercel domain: https://samo-deloru-sromans-projects.vercel.app Problem The vercel.app domain works perfectly: loads instantly full HTML delivered correctly no transport issues But the custom domain behaves differently: HTTP 200 returned successfully TLS handshake succeeds HTTP/2 connection establishes correctly response starts downloading then the response body stalls/truncates and times out Important This is NOT: DNS misconfiguration SSL issue Cloudflare proxy issue middleware/rewrite issue application logic issue Cloudflare proxy is completely disabled (DNS-only mode). The exact same deployment works normally on the vercel.app domain. Diagnostic findings Example curl/debug results: Expected content-length: 62353 bytes Actually received before timeout: ~5921 bytes Error: Failed receiving HTTP2 data This reproduces consistently across multiple Vercel edge IPs: 216.198.79.1 216.198.79.65 216.198.79.129 216.198.79.193 64.29.17.1 64.29.17.65 64.29.17.129 64.29.17.193 TLS/HTTP2 details: TLS handshake successful HTTP/2 established successfully content-length correct body transfer stalls during delivery Ping to the edge IPs works normally with low latency and 0% packet loss. Additional info Environment: Next.js App Router deployed on Vercel no host-based redirects or rewrites no Cloudflare proxying DNS points directly to Vercel The issue appears specifically related to custom domain HTTP/2 body delivery / edge transport. Has anyone encountered similar behavior with custom domains on Vercel? Any ideas or workarounds would be appreciated.