Harmy said:
As it has the same colour as the lightsabre element and it appears in Puggo Grande as well, I'm pretty sure it is some error made in the making of the lightsabre effect, so that's why I restored it.
Not every flash of light in PG (or PSB) is necessarily original. There is a strange flash that appears in one 16mm ESB print but not the other, for example - Adywan noticed it. (not sure about the particular one referenced above, though).