its much too small
try gumball shift click on one and resize by 1000. then use fitsrf on that messy surface with 3 and 3 degrees and 0.1 value (tolerance) that should simplify the surface within a usable range, just try if thats ok for you. after that use your shortpath and shrink it down by 0.001 again if you must.
one side of the surface is open it may have done a short path along the open surface because it was far too small first. see if the file helps you. i attached the file resized to x1000. working in that small space will always cause problems in general.
problematic_shortpath-2.3dm (2.8 MB)