Your videos are hard to watch, you move around too much. Keep camera in one spot for each video, but I think I see what is going on, and the guys are right, you need to roll back FLUX Studio for now.
Test #4 @ 1:07 It is the Mini USB cable that is pulling back on the front left and rear con rods when at full extension during the circle movement. The Delta+ has a redesigned cable and it appears to be stiffer than the original. If you slow that video down and watch from 1:07 - 1:11 you can see the stress and release from that cable.
I would not even bother with any of the 0.7 releases at this point. Go to the RIGHT side of the downloads page and get 0.6.3 under the Latest Stable Releases. You are passing calibration, and 0.6.3 doesn't have the racetrack movement. As long as you don't try to print anything at max bed size, you should be able to get started until FLUX Support gets it sorted out.