When using a VFL (visual fault locator) to check the integrity of a pigtail or terminated fiber, light will leak out of the cladding portion of the glass. This is normal. The VFL light has an overfill launch that will surround the core and extend into the cladding.
Depending on the type of connector and fiber being used, more or less light will leak through. The light will be significantly more visible in the lighter colored 900um fiber cables. When using APC connectors on the pigtails or terminated fiber and a standard PC connector from the VFL, more light will be visible / leak through because the different polishes.
In position 2 on the connector, the light should be dimmer than or show no light than position 1. The reason for the light variance in position 2 is the fibers may not be perpendicular. If the light in position 2 is equal to the light in position 1, you can "tune" the fiber by pulling out fiber slightly and slowly twist until the light dims. Once the light dims, reinsert the fiber until it bends and release the wedge clip.
To make sure that the termination is good, check the end of the pigtail/ fiber. If there’s little to very little or no light at the end of the pigtail / fiber, then there’s an issue.