Potential Vulnerabilities in Sync Encryption

I've been testing a few popular sync tools and noticed that some of them use a custom encryption layer on top of TLS. Has anyone audited these implementations? I'm concerned about potential downgrade attacks.

We've performed a third‑party audit on SyncPro's encryption and found that the custom layer adds negligible security benefits while increasing complexity. I'd recommend sticking with end‑to‑end encryption using well‑known algorithms like XChaCha20‑Poly1305.