DNA testing: not reliable afterall

Genetic Chimera is a known condition where a person has 2 sets of DNA inside a body [apparently due to absorbing DNA from twin sibling] such that it is possible to have normal DNA test mismatch with your own children's DNA's.

So much for DNA as a proof of identity. And yet another defense against any given DNA evidence.

And, what other problems with DNA testing that we don't know about?

[Saw this in ABC news just now and then googled to find wikipedia info].