I finally successfully got these creating new Eclipse workspaces, whew! Unfortunately the tests fail in the exact same manner both inside Eclipse and when run directly via Maven. I'm really at a loss for what is different between the two runs. The source data file inpop10b_TCB_summer_1969_bigendian.dat shows up identical in both my orekit-6.1 folder (which I got from a zip download and in the directory that was pulled directly from the repository. The function that reads it, JPLEphemeridesLoader.readInRecord are identical between the two versions. That should mean that the byte array it loads should be identical. However for some reason somewhere after byte 2600 they start diverging. That is the ultimate source of the error. How it is happening, I have no idea.
I'm still using JDK 7. At this point I'm also fighting Eclipse, both on Linux and Windows. If I try to build multiple workspaces pointed to different source directories using the "Existing Maven Projects" import method it fails with some bizarre errors. I have to end up blowing away my entire .eclipse and .m2 folder to have a prayer of it sucessfully building the new workspace. So I'm wrestling multiple things at the same time, unfortunately. Once things settle down I'll start debugging this again, assuming it doesn't fix itself.