I tried importing one of my textured models as a Collada file. This was packaged as a zipfile that contained a “model.dae” file and a folder called “model” that contained the three texture images I used in the model. Importing the model into 2008, 2015, 2016, and 2017 gave me these results:
I’m reminded of a similar post regarding STL imports:
Using “Soften Edges” doesn’t hide the lines, nor does anything else I’ve tried. However, if I select each line or use the eraser, I can make them go away:
Model file: 3D Warehouse