No, that's reading too much into a story.
The National Archives is not investigating anything. They commissioned some people to produce a new tape of the dictabelt using a technology that won't damage the original.
They've done so because a number of people have recently made requests for copies of the dictabelt and the Archives has been unable to fulfill those requests.
Last year was the 40th anniversary and Court TV was unable to obtain a copy from the Archives for the show they did about the acoustics evidence. Others have also asked. They were able to complete their work by using the older copies we already have.