I'm still unable to duplicate.
I deleted the old Custom Device and started over. I created a new one with 14 attributes, from powerMeter to energy.
I don't have a HEM, so on a Remote Hub, I created a virtual device using the built-in 'real' driver: Aeon Home Energy Meter. I then mirrored that back to the Server.
No errors. So then I did a refresh and a Config on the 'real' device on my Remote Hub. Again, no errors:
app:193 2020-05-17 10:20:18.475 am info Received device update request from server: [308, type aeotechomeenergymonitor]
dev:308 2020-05-17 10:19:57.307 am debug [7004650400000004, delay 100, 70046F040000012C, delay 100, 7004660400000008, delay 100, 700470040000012C, delay 100, 7004670400000000, delay 100, 700471040000012C]
app:193 2020-05-17 10:18:53.273 am info Skipping event subscriptions... Using event socket to send events to server.
app:193 2020-05-17 10:18:52.763 am warn The device [pseudoHEM] does not support the command refresh.
app:193 2020-05-17 10:18:52.747 am info Received command from server: ["pseudoHEM": refresh]
app:193 2020-05-17 10:18:50.968 am info Sending custom devices to remote: aeotechomeemergymonitor - [[id:308, label:pseudoHEM, attr:[[name:power, value:null, unit:W], [name:energy, value:null, unit:]]]]
app:105 2020-05-17 10:20:17.890 am debug Requesting device sync from ZeeFourth: pseudoHEM
app:105 2020-05-17 10:18:52.231 am info Sending refresh command to HubConnect Server.
app:105 2020-05-17 10:18:50.839 am trace Creating Device HubConnect Aeotec Home Energy Monitor - pseudoHEM... 192.168.7.65:308...
Because I don't actually have a 'real' device, there's not much in the Driver Info page to click.