The problem is already known by developer Apehum.

Unknown how to reproduce, however it happened when the player who had the crash was standing not so far from me.

When this happened, I minimized Minecraft window and went AFK for a few minutes. I come back and the player tells about the crash.

https://mclo.gs/nrAYOxF got crash, maybe it's helpful?

@le0nlol Hi! Any way you can send me your iris/sodium/etf/etm configs?

The issue was found and fixed in e635fcc.
You can download the latest snapshot build with the fix here: https://github.com/plasmoapp/plasmo-voice/releases/tag/2.1.6-SNAPSHOT.