Unpredictable results from Knife tool

I am getting different and unpredictable results every time I use the Knife tool.

I have looked around for posts on this.

I am cutting a simple subdivided plane with all verts merged.

Sometimes the knife cuts from an edge to another edge, sometimes it doesn’t.
Sometimes the knife cuts from an edge to a placed point, sometimes it doesn’t.

The screen shot shows one of many different cuts I get from trying to knife across some faces. The yellow circle shows where it has created a new vert just of an edge I was snapping to.

Any suggestions please?

I might have answered my own question and this might be to do with my View / Clip setting.

The subdivided plane is an environment with the main square sections measuring 20x20m.

When I was having problems with the Knife, my View Clip was set to 2mm. When I increase this to 2m I get much more predictable results with the Knife.