This means you had a syntax problem in your serialization/deserialization, check the Gson javadoc to check the right syntax: https://goo.gl/g7LnZb
This seems to be a bug in the-blue-alliance, fixed in version 4.2.3 (link for github in case you want the changelog: https://goo.gl/NQAKUf ). If you're not using it, it might be that you're parsing xml as json.
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