Ok, I guess, one last suggestion...rotate the model 90deg (z-axis) on the bed. Does the line move from the front to the left/right? If so, its the model. If not its gotta be something in the slicing or possibly machine. From prior comments, I don't think it will make any difference. You said when you chose random start positions, the same effect (a gap) appeard all over the model? Yes? If so that says slicing as well. It also seems to eliminate mechanical slop (loose belt for example) which would show itself in a particular axis.

I presume you covered the basics like making sure the filament diameter, nozzle diameter, etc are set correctly in the config file for the slicer. I am out of ideas if this doesn't cover it. I just don't have the experience yet to get any deeper. I am still new at this too.

Why not download Cura and KissSlicer and see if either does any different than slicr?