You are right, It destroys my faces... well it splits them into triangles but they stay planar... so I just have to delete the created lines manually. I can live with that But the bad thing is that rounding coordinates does not solve the problem I have... It seems to be a known bug! It happens with complex models when you often change the axes with the axis tool. I need some way to re-align edges to the axes (even their start and end-points are (almost) exactly on one axis, they are not recognised so)