first some things that i do know:
the once in a while erratic ejection can be from what is termed "extractor clocking", this is when the tolerance between the firing pin stop and the extractor slot is to great....allowing the extractor to bit by bit ever so slowly and erratically rotate. this changes the "grip angle" if you will, that the extractor has on the case, and this causes different ejection paths. also a recoil spring which is too weak will cause erratic ejection.
from what i have read, 3 to 6 ft...to the right and slightly behind is acceptable.
additionally as an earlier writer stated, improper extractor tension can also be a problem. the shop manual i use says that with the slide off, the extractor should be able to "just hold" a loaded round while swinging the slide from side to side.
basic ejector geometry is something like this:
with the slide off and the mag well empty, if you place a small flat piece of whatever (like a ruler) in the mag well and press it against the back of the mag well, that is the proper primary angle and starting length.
additional cuts with the file make a flat about .050-060 on the front end. when done it should have a small rectangular face with a relieving angle on the same incline as the mag well. finally a very small 45 degree cut on the inner corner of the above mention rectangle.
i hope this makes sense and helps