Powertip E with smart placement not showing tooltip when element next to browser right edge

[evbrew]

What it says.
I have a table with text inputs in the cells.
Table is wider then the browser window.
The inputs in the last column do not show the tooltip.
If in debug mode i make the size of one of the inputs in that last column smaller so its not right up against the edge then the tooltip appears for that smaller input only (W placement).

Console logging the getViewportCollisions function, it correctly deduces collision for E, NE, SE but then it tries W and for some reason returns a collision (my tooltip is pretty small, maybe 40x40 pixels total - smaller then the input field which has size 50). It finally returns N as no collision, but still doesn't show anything.

[evbrew]

ok, i figured out a little more, the tooltip is now showing up in the N placement but about 80pixels too high above my element. Not sure if that is just an issue with N on that element or indicative of something else.

What i would like to understand is why the smart placement is calculating N instead of W in this case?
I have a test fiddle here, if you mouse over the last column of the table you will see the placement be N instead of W.
https://jsfiddle.net/uhcL2b6k/