[Paraview] 3d Contour plot on cylindrical grid - inaccurate contours with prefered direction in toroidal angle

[markus]

Dear all,

i'm for a long time experiencing a contour plot problem in 3d. Our 
scalar data is on a cylindrical (R,Z,\varphi) grid. A 3d contour of the 
data produces correct "2d contours" in the RZ plane, but the contours 
are elongated in the \varphi direction, even if the data prefers another 
direction.

Image here:
ftp://ftp.uibk.ac.at/private/c7441143_20170403_7512b21ed0886d37bdf38b41d4056946

The prefered direction is aligned to a given vector field.

Is there a way to improve the 3d contours with a filter in paraview or 
maybe with the help of the given vector field?

best regards
markus