Spin cycle doesnt spin out the clothes/drain the water?

Our LG WM2077CW washing machine that we purchased at a yard sale worked when we first brought it home. But now, when you wash clothes, it will go through all the cycles no problem, until it reaches the final problem, the spin cycle. When it reaches the spin cycle, it just sits there not doing anything, which causes the clothes to just sit and soak in the dirty/clean water. At first, we thought it was just a minor bug that we just needed to unplug the machine and let it reset. But it still wont spin. Let me be clear though, the drum spins on every other cycle in which the drum should spin, but during, ironically, the spin cycle, the drum wont move.