Hi @cr.stubbs
I wanted to revisit this post from a few months back and see if you would mind trying this tutorial I just wrote up on how to convert your sketch file from our Cayenne Arduino Library to Cayenne Arduino MQTT.
We believe this MQTT connectivity is more stable and fault-tolerant than our original Arduino connectivity and would be interested to hear if you see that as well and if it improves the connectivity issues you were seeing. Please feel free to contact me if you have any questions or need assistance with converting your code following the steps in that post!