The Shroud ‘failed’ the carbon dating tests, but it used an edge that could have been re-woven. Or, the resurrection process may have altered the makeup of the cloth.
The samples used for the carbon dating were all taken from the re-woven area. AFTER everyone had already agreed that this was the one part of the Shroud *not* to take samples from.
Second, the testing was done at three different labs. All three labs gave different ages for their own sample: and the age given by each lab, was outside of the error bars of the other labs.
Can you say “systematic error”?
The former.
And, as you suggested, the portion selected for use in dating the shroud had been expertly, diligently, and reverently rewoven many centuries ago.