Fast way to check overlapping faces is to ctrl+a to select all vertices and then weld them with a threshold on 0,01 and if its a change in the before and after number you got overlapping vertices.
I had this issue the other day, make sure your vertices are all welded. I had a lone vertex hanging out in the middle of an edge and it was messing my swift loop up.
it has 5 verts but fixing that did not fix the issue (thats why I left it this way). @Kbrom, yes this is what I thought also but I could not find overlapping vertices. Is there a fast way to check ?
thanks guys! it turns out there were some hidden vertices that sneaked themselves into the model. Also quads is the way to go idd. @Velktri, I had that problem before but luckily I am not that sloppy anymore =P Learning the most from making mistakes! ^^