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When i was creating the gcode for this with slic3r, it came up with the error "This model has overlapping or self-intersecting facets" and "the input file was not marnifold near edge 122.000000-121.000000." When i printed it then it started printing from the layer above the front arch of the ballista. Any idea why this is happening? I printed the catapult the other day and its fun as hell, so i'm dying to get this one printed! Thanks!