Store axis as MultiLinestring MultiLinestrings could already be imported but we stored them as multiple Linestrings with identical attributes and even stored Linestrings with self-intersections as multiple single Linestrings with identical attributes. Avoid both by storing as MultiLinestring. In passing, removed unnecessary processing steps in the INSERT statemet for the sys_admin case and ensured that attempts to convert to valid simple features are made after transformation, which might lead to invalid features. Since isrsrange_axis() relies on single Linestrings for linear referencing, add an extra ST_Dump().