vS, uS, and u5 are documented readings of a possible vibration sensing anomaly in LG front-loaders. They are not the same as a UE unbalanced load error.
The LG chart recognizes these display variants. A photo helps distinguish the letter S from the number 5 and preserve the message for support.
What you can check with that information
Note whether the alarm appears at startup, during a slow spin, or while spinning at full speed. See whether it repeats with different loads you have already used; there is no need to run new tests to get a repeat.
Adding clothes can be a measure for certain imbalance conditions, but it does not verify a vibration sensor. If your manual allows you to resume or reset, follow that recovery step once and check the result. Recurrence calls for investigating the sensing system and connections.
Do not remove panels to move connectors or replace shock absorbers because of this message. Poor support may exist at the same time, but seeing the machine vibrate does not prove which component triggered vS.
Give the technician the display image and the recorded stage; keep the distinction between a balancing issue and a sensing alarm.