Lg front load washer WM2301 will not drain

My washer doesn't seem to drain and I'm getting a OE error. I have drained the tub from the front drain, and then it works, but it's not draining out the back. The LG customer service thinks it might need to be leveled, but when I check the level it seems fine. Could this be a problem because I have it installed on the second floor of my house?

Drain hose may be bent or clogged, or the drain filter itself may be clogged