Keep in mind, this is the same experiment Eagleworks did all those months ago. There are still plenty of experiments left to do, and we're still months away from determining even if it works, not to mention why.
Luckily, if they can get the thrust high enough, Goddard said they'd take a look, which would be a good source of independent verification of their results. Lots of wierd shit is supposedly found that later turns out to be error, see tons of new particles that were thought to be discovered at 3 sigma significance, to later be a statistical anomoly and the FTL neutrinos that were caused by a wiring error.
As with anything in science, it has not been proven to work, only to not fail, and continued experiments will try again and again to show how the device actually doesn't work, and it's just some source of error unaccounted for. It's important to be sceptical, exciting news as this is, particularly when what is experimentally observed contradicts a fundamental cornerstone of physics. This will be a process that takes years and years and years, and every experiment will have to be exhausted before we can definitively say it probably works.
Edit: As someone else pointed out, there has already been a future test stating it may have been electromagnetic interaction with an outside source causing the thrust. Future tests will have to take that into account.