MQTT JSON/Protobuf errors

Hi Guys,

I have installed a new version of Chirstack (v4) and I am getting errors with mqtt messages. in the chirstack log I see the message received from the gateway:

INFO chirpstack::gateway::backend::mqtt: Message received from gateway region_id=“as923_4” topic=gateway/34fa40fffe1e5418/event/stats qos=AtMostOnce json=false

And then receive an error straight after:

ERROR chirpstack::gateway::backend::mqtt: Processing gateway event error: failed to decode Protobuf message: GatewayStats.rx_packets_per_modulation: invalid wire type: StartGroup (expected LengthDelimited) region_id=as923_4 topic=gateway/34fa40fffe1e5418/event/stats qos=AtMostOnce

Is anyone able to point me in the right direction to diagnose?