DIAGNOSIS Faulty or overheared Wi-Fi module in the TV, or interference from the TV's own components.
FIX Forget your Wi-Fi network on the TV. Restart your router. Reconnect the TV to the 2.4GHz band, not the 5GHz band, for a more stable connection.
IF THAT DIDN'T WORK Use an Ethernet cable. The 55U8K has a 100BASE-T port. If the problem disappears, the internal Wi-Fi card is likely faulty.
HEADS UP If using Wi-Fi, in Settings > Network > Advanced, set the 'IP settings' to 'Static' and manually enter your DNS as 8.8.8.8 and 8.8.4.4. This can prevent DHCP drops.