MQTT protocol error on bridge

Look at this log. Its my bridge for ferroamp.Everything works but i have this error. Cant find anything with google, chatgpt or the docs.

Thoughts?

2024-12-07 17:43:43: Connecting bridge ferroamp_bridge (192.168.1.9:1883)

2024-12-07 17:43:43: mosquitto version 2.0.18 running

2024-12-07 17:43:43: New connection from ::1:55452 on port 1883.

2024-12-07 17:43:43: Client disconnected due to protocol error.