Diagnosis
This is a streaming latency issue, not a recording problem. The two video streams are taking slightly different data paths to your phone, often because one stream is being processed or prioritized differently by your network or the eufy servers.
How to Fix It
First, check your local network. 1) If you're on Wi-Fi, try moving closer to your router. 2) A quicker test is to switch your phone to cellular data (if you have a strong signal) and see if the sync improves. If it does, the problem is your home Wi-Fi congestion. Try rebooting your router and any network switches. The goal is to give both video streams a clear, fast path.
If That Didn't Work
The issue might be within the eufy app's cache. Force close the eufy Security app completely on your phone, then clear its cache (on Android: Settings > Apps > eufy Security > Storage > Clear Cache; on iOS: offload and reinstall the app). Log back in and check the live view. This clears out temporary data that might be causing a playback bottleneck.
Heads Up
When you review recorded events, they will be perfectly synchronized. This sync problem usually only affects the *live view* stream. If you need to monitor in real-time and the delay bothers you, try viewing only one lens at a time in full-screen mode, which often reduces the latency.