The UE code appears due to unbalanced loads. Once it occurs, the system stops the drum to prevent damage.
To ensure that you load the right amount of linen, study all modes and cycles before loading your machine. Big and heavy itemd become heavier in water and may break the balance. If you need to wash a big item (a blanket, large towel, etc.), add a couple of smaller ones for better spinning.
If there is the UE error, and the door won’t open, run a drain mode. You can do it by pressing the Spin button, as you choose between a spin (the spin symbol with a line) and zero (no spin).