The balls inside the nut rotate in the nut, every 3..5 rotations of the spindel. The nut is preloaded. A wrong diameter (to large) ball could be the cause but the effect would be largely compensated by the other balls.This wave reminds me balls inside carriage how they rolls, just my guess ?
The balls inside the carriage rotate in the carriage, every 4..6 rotations of the spindel. The carriage maybe preloaded. A wrong diameter (to large) ball could be the cause the effect but the carriage would move in Z direction.
The 20° edge shows deeper indents at a shorter interval. The interval is about 1/5 of the thickness (15 mm), so every 3 mm at 20°? That is about 8.24 mm at 90°. That "fits" the 10 mm pitch ball screw!
Have you checked the straightness of the ball screw and measured the runout at both the machined ends?
If you remove the BF bearing and position the part close to the BF side, is the result better?
With the carriage moved closely to the BF size can you measure the runout at the end of the ballscrew?
With the carriage moved closely to the BK size can you measure the runout at the end of the ballscrew?