AppSearch: Error during document insert. "There was a decoding error. Please ensure your request is valid."

Error Message: "There was a decoding error. Please ensure your request is valid."
I am receiving an error while inserting document. I am within the limit and this is occurring randomly during a large insert process where we are inserting a couple hundred thousand documents into AppSearch. The majority of the insert requests, which are the same, are completed without issue. But every once in a while, we get one of these messages. The api logs don't show a 400 and we can't find anything wrong with the data in the requests or the request itself. Have anyone seen this issue? Any thoughts on the error message or further insight on why it is thrown?

This error is received back when there is a JSON error or URL parameter encoding in the request that is not correct. You can see the API reference for the error diagnosis.

API Logs should contain the requests done for inserting the documents. Are API Logs enabled?

In case API Logs are not available, logs/system.log file in App Search contains web requests and response codes that can help you evaluate which specific documents are the problem.

Not sure how I missed your response. API logs are enabled. I still haven't tracked down the issue since the requests are valid and all the documents in the request are inserted correctly. We are upgrading soon and will revisit once we are on the latest version of Enterprise Search.
Thanks the the response.