The UL error code stands for “Unbalanced Load”
If the load is not well balanced, the washing machine will try to correct the problem at the end of the cycle. If the recovery is over, but the code is still there, you will need to open the machine and redistribute the load manually. When you have done that, close the lid and launch a cycle.
If you are sure that your loads are optimal, and the machine displays the error regularly, you will have to reduce loads at least by half. Most likely, the suspension spring rod kit is down and needs to be replaced.