I just had the transfer case replaced, leaking trans fluid now. Any relevance?

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I just had the transfer case replaced with a used one on my 2004 Ford Explorer 4.6L V8 and now it is leaking transmission fluid, same night after the work was done when it did not leak transmission fluid prior. Can there be any relevance to why it is leaking transmission fluid since the transfer case was replaced? Shop is telling me it is pure coincidence.