Severe lip sync and latency issues in UE 5.7

Unreal Engine Questions
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1

see to video: Video convai

pass: 1234

Hello, I am writing because I am extremely frustrated with the current reliability of the plugin, and I urgently need your help.

At this point, every time I solve one issue, another one appears. This is seriously affecting my work and my credibility in front of clients. It is becoming very difficult to confidently present a product when I do not know whether it will work properly the next day or fail during a demo. That puts me in a very embarrassing position and damages trust with my clients.

The issue that is bothering me the most right now is the lip sync and facial mouth animation during speech.

Almost every time the character speaks, the audio plays, but after starting correctly for a brief moment, the mouth stops animating and gets stuck in a strange position for the rest of the dialogue. Sometimes it stays open, sometimes closed, and sometimes twisted in an unnatural way until the line finishes. This makes the avatar look broken and frankly ridiculous in front of the client.

I have attached a video so you can see the issue directly.

In addition to that, response times are often extremely slow. Some days the system performs relatively well, and other days the delays are unacceptable. I do not understand why I have to wait around 5 seconds for my request to be processed and then another 5 seconds for the response to begin. And when the response finally comes, the lip sync is often still broken.

From the client’s point of view, there is no technical nuance here. They only see one of two things:
either the product works, or it fails.
If it fails, they do not pay, or they ask for a refund.

That is why this is not a minor inconvenience for me. It is directly affecting deliveries, confidence, and commercial viability.

I have already spent a lot of time reviewing the forum and testing the recommended workarounds, including:

  • Extra parameters such as: MinBufferDuration=7, AudioLipSyncRatio=0.5, EnableSync=1

  • Reinstalling the plugin

  • Testing with different audio inputs

  • Testing with different languages

  • Testing with different AI models

  • Creating a completely new project from scratch, etc…

None of these attempts has solved the problem.

My setup:

  • Character ID: ca81221e-1232-11f1-88c2-42010a7be02c

  • Unreal Engine version: UE 5.7

  • Convai version: 4.0.0-beta.14

I am using the latest beta because every time a new update is released, I expect it may solve the previously detected issues, but at the moment I still cannot achieve a stable and professional result.

Please let me know:

  1. Whether this is a known issue

  2. Whether you already have a fix or workaround for it

  3. What exact steps I should follow to solve it

  4. Whether this problem is related to the current beta version

I would really appreciate a clear and practical solution, because right now this is affecting real client presentations and making the product very difficult to trust in a professional environment.

Thank you,

2

Hello,

Please upload the video to a place where we can view it directly without needing to download it.

Also, the version you are using is a beta release, so issues like this can still occur. Improvements and fixes are being made continuously. If you need a more stable experience, I would recommend continuing with version 3.6.9 for now.