Power Factor bouncing between -1 and 1 (or is it?)

Introduction

If your power analyser is measuring between -1 or 1 (actually 0.99 and -0.99 like below) it is actually a good thing (inverter performing well):

Reasoning

It is not actually -1 and 1 it is more like -0.99 and 0.99. The inverter is trying to inject PF of 1 but it is not perfect (obviously nothing is ? ) so it is bouncing around 0.99 (very close to 1) and -0.99(also very close to 1). 

See below drawings of both leading and lagging. The lagging is 0.99 (with the green arrow as small as possible), the leading is -0.99 (with again the green arrow as small as possible):

-1 power factor is actually not a bad thing, it is 100% real power still (just power flow in the other direction like below (with the green arrow = 0):

Since I am waffling let me continue. The sign in front of the magnitude is also just selected by the person doing the calculation. As long as the logic is held through the whole calculation it will be fine. Generally us as a PV inverter call positive power export and negative power import. However distribution networks would consider it the other way around (mind blown).