Seam in the 360 degree picture of a Theta V camera

My recent 360 degree images taken with my new (< 1 year old) Theta V camera started having a seam. The seam is visible where the projected 2D image is glued together for a 3D full sphere image. I.e. the left and the right edge of the 2D image are not properly closed any more. An example is in the image uploaded here: the seam is visible as vertical white line. The camera has worked fine for many images up to now. What is the reason for this seam? How can I get it fixed for future images?