I wonder if your Smart TV received an update causing th changed behaviour.
To test your hypothesis, can you run a temporary Ethernet Cable to the TV?
Do you happen to have a Sony Bravia TV? I have encountered this issue in the past and I narrowed it down to a defect in the Ethernet driver or firmware. It seems to related to power standby mode. A reboot sometimes fixes it for a while. Maybe try adjusting the power settings.
It resolved itself with a firmware update sometime later as I haven't seen the issue in over a year.
Some info here as well: