A model number would help with a more specific answer but there are a couple of things to consider.
Under certain conditions a combination of the wash load, cycle selection and movement of the clothes during the cycle can cause the load to become twisted, tangled and balled up.
First check the drain hose is not stuck to far down the standpipe. Sometimes this problem was caused by the drain hose being to far down the pipe and creating a siphon action. During the wash water would siphon out and with no water the clothes would twist into knots.
Load the clothes in a loose heap more around the impeller than directly on it and don't overload the washer.
Finally on certain models the wash impeller was redesigned to have less chance to cause this problem. The new and improved impeller is part number W10077050 and it would most likely help your washer reduce the amount of tangling.
If you have the model number and submit another question I can tell you if your specific washer model was part of the impeller redesign.
I hope this information helps to resolve this problem but submit another question with any additional details for further assistance.