If IoTaWatt were not connected and able to communicate over WiFi, there would be log messages indicating failure to access time server for 24 hrs, or inability to access the update server. There are a couple of random network server failures, but that’s over a month and it does so every hour. There isn’t really any difference between outbound and inbound TCP from a hardware perspective. It’s just packets.
You are running the same firmware as thousands of other units, and it is validated with an md5 hash when installed, moreover there has been a firmware upgrade and the problem hasn’t changed. So I’m ruling that out.
So that leaves something in your environment. I have an IoTaWatt in an outbuilding. It connects to my WiFi through a WiFi bridge. Sometimes the connection between the bridge and my router gets disconnected and I can’t access the unit for hours or days. Then the link is restored and voila, it’s there and catches up on all it’s uploads. The unit itself does not log a disconnect because it’s connected to the bridge, but I can’t access it.
I’m not saying that’s your problem, but just demonstrating that there can be LAN issues that manifest themselves as routing problems.
If you have another WiFi router or AP you could try, or perhaps a phone hotspot, that might shed some light. If you are convinced the unit is somehow defective, you can send it to me and I’ll check it out.
PO Box 1679
Wolfeboro, NH 03894
If you do that, send me a PM with a tracking number.