In the Edit window, have you tried Select Inverted Polygons in the Select menu? This should select only the mirrored UVs, but it could also select badly-mapped UVs too. Then you can Break them.
The "Symmetry" plane you saw is merely the preview for the Quick Planar Map gizmo. By default it faces the average of the selected surface normals. Selecting both sides is weird though. Could be both were inverted.
I have some Mirrored UV's in 3DS Max that I am trying to flip however when I select them in the Unwrap modifier it selects both of them and in the viewports it shows a mirror modifer similar to the Symmetry gizmo. Is there a way to break the mirrored UVs apart so I can flip the correct ones? I have tried the "Break" tool…
Hey Eric, I did try selecting only the inverted ones however it selects both sides and in the viewports it shows them highlighted in red with a "Symmetry" plane between them. I am not sure if its cause I mirrored them then opened the obj up in Headus then opened it back up in 3DS Max. What I ended up doing was redoing the…