Getting rid of white noise with 99% converged ratio

Hello !

I'm learning Daz and I'm having a problem with remaining white noise even when setting a 99% converged ratio

here's an example :

here's another on a different surface / lighting condition (taken at 30% just to show it even more explicitly)

I'd like to know how can I get rid of this, or at least make it less problematic. Usually around 75% all of the rest of the image is rendered quite good except those areas with white noise, that leads me to believe I do something wrong when setting up the scene or in my render settings, and I should be able to to have quicker renders / better quality overall if it's possible to do something. This problem happens in a wide variety of environments, but i didn't find any easy culprit (well lighten or in the shadow, dark or light surface, flat or rounded, glossy or not etc ..., but I've surely miss something).

In this scene (but it usually appear in most if not all of them) I mainly use ghost lights (I guess it's my problem but it's so useful and easy I'd like to find a work around) and a few built-in lights that comes with the scene.

Here are my render settings (everything not specified is default) :

- Pixel size 2560 / 1440

- Max time 28800 / Rendering converged ratio 99%

- Shutter speed 150 / F Stop 10 / Film ISO 130

- Environment Intensity 0

So if you can give me a tip or two, I'd be really grateful; thanks in advance !