It appears some textures do not get the gearvr AA method that used everywhere else. Lines are swimming everywhere 
Occurs often with textures designed for UMG widgets placed in 3D space since they often have lines and text in them.
The UMG widget itself has a few images inside it (where the images are simple textures) - and it renders very noticeably with no AA it for both Masked and Transparent rendered widgets.
Tested on: 4.11 preview 5 (assuming the same on older versions as well)
Let me know if you require any further information!
Answerhub query here: https://answers.unrealengine.com/questions/375974/gearvr-aa-not-working-on-umg-3d-widgets.html