Can you isolate it to find the root cause? I assume it's not the model if it's happening with 2 different models. I suggest comparing against
https://github.com/livekit-examples/agent-starter-python/blob/main/src/agent.py as a baseline, then introducing your custom agent logic to find the source (prompt length, turn detection).
You say "While using Livekit inference", but I assume this doesn't go away if you use the plugin.