I understand your frustration and would even agree that this machine had more issues than most. It was the first top load washer that tried to use very little water like a front load.
I can tell you how to fix the washer but your last sentence where you ask "if or how to fix it?" makes me think you are not sure the washer is worth repairing.
That is a good question and your instincts serve you well.
The 285990 pump cost $141.82 dollars.
This is not cheap and knowing what you have in mind would help. I think you already have a replacement washer and just want to fix and sale this washer.
The first thing I suggest is to check the drain pump hoses for socks or other objects that might jam the pump.
You can try a drain and spin cycle to see exactly what the pump is doing. Listen for a hum or buzz from the area of the pump.
You can check your paper for ads from companies that by broken appliances. You could sell it broken for $25-$50 dollars and have it hauled away.
From the history you have had with this washer you might like that option.
Give me a reply with what you wish to do. Do you want to fix it and sell it or do you need a washer in your own house?
I'm sorry you had such a bad time with this washer but let me know what you really want or need from this washer at this time and I'll help you the best I can. .