I have never, ever seen this in the Window Camera.
And trust me, I've spent my fair share of hours (like... too much) with the window camera for virtual photography.
I don't recall a graphic option either for flares (even in the past), and the only possible solution is the dust/halo option in a light, and it does not look at all like that.
I would recommend to create a temporary fresh install of VAM and test it. Honestly, I'm like 99.81% sure it's not Vanilla VAM.