WATER POOLS UP IN WASHER OVERNIGHT
Siphoning, or a water inlet valve problem can cause this problem. Siphoning occurs when you have your drain hose inserted into the standpipe too far creating a vacuum. Not only does it cause problems with the washer's ability to maintain proper water levels, it can also cause back flow from the drain into the wash tub. Check your drain hose by lifting it up from the standpipe. You do not want the hose resting in the drain trap. You need an air gap to proper drainage. Do not seal the top of the standpipe and make sure the drain hose should be placed into the pipe about 4 to 6 inches only.
If you check the drain and it is fine, more than likely your cause is a leaky water inlet valve. The solenoids in the valve do go bad and can leak by, causing the washer to fill slowly during periods when it is not used. The valve is easily replaced by removing the washer top panel and shutting off the water supply. There a couple of mounting screws and dispenser hose to remove and thats about it.
HINT: A simple test to determine which one may be causing your problem would be to turn the water lines to the washer off for one night. If the problems goes away, you likely have a a water inlet problem. If the problem persists, you know you probably have a drain problem.
I hope this helps you. If you have questions, please let me know.