Is it possible sendgrid's system or Swiftmailer could be garbling my code?

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Has there been any reports of Swiftmailer or the sendgrid system messing up the code of an email? One of our templates that we have used in the past (not through sendgrid) has large areas of code duplicated many times at the bottom of the email. When tracing the code during the send process it displays fine and other emails we have sent with a different template have worked. There is something about this one template that is getting VERY wonky when it foes through sendgrid.