I'm trying to manually edgematch some adjacent polygons. When I try to add a vertex to snap it to another vertex on an adjacent polygon, it invariably undoes itself, as shown in this video that I made demonstrating the problem (I couldn't figure out any way to post it here since it is not an image so the best I can do for now is a link).
There are 2 vertices in the beginning and I add a third. It is actually removing one of the 2 vertices on the right side and putting the result in the middle. It must be a tolerance of some sort but I tried changing it from 10 pixels to 5 (or 3 or 1) pixels and zooming way in and the problem still occurs (it just becomes more difficult to find the snap point). Is there any other setting I could modify to force the added vertices to snap without moving the other placed vertices?