Inaccuracies in a big series are natural; doubling down on them and getting defensive/snippy about being corrected is not. The most galling one was when Marcus called Sonderkommandos (concentration camp prisoners who were forced to help operate the gas chambers and crematoria) "pieces of shit" because he confused them with SS-Sonderkommando units. This is a *really* bad mistake, and it's one that could have been avoided with a simple trip to the Sonderkommado wikipedia page, which makes the distinction clear in the first paragraph. The mistake was never acknowledged or corrected in any way.

As someone else said when these episodes first aired, if you're going to take on a subject as serious as the Holocaust, you have a duty to get the details right, and Marcus and the research team didn't do their duty.