Chirpstack packet transformer - "UPLINK_CODEC" "error"

Chirpstack packet transformer - "UPLINK_CODEC" "error"

We are trialing the "Chirpstack packet transformer" option for our MQTT connection however, with this enabled we get the following for any MAC data up commands:
{ "devEUI" : "xxxx", "deviceName" : "xxx", "type" : "UPLINK_CODEC", "error" : "either driverId or thing.application must be present" }

When we remove the packet transformer the full information is there. It does have this same error in "payloadDecodedError" field but it still has all other fields including "payload_hex".

Is there extra configuration required for connection or end-devices to work with the Chirpstack packet transformer? Has anyone else had issues with the Chirpstack packet transformer?
We are looking to just get the raw payload and not have it decoded inside Actility  since there is no driver for our custom device at this stage.