QGIS » QGIS Application

I'm using QGIS 2.18.13. Been working on a project for some hours now.
I had some project filec orruptions - not sure what the issue there is, assuming virtual layers.

But here's a bug I can reproduce easily in my current project.
I have a virtual layer (currently simply selects all features from a shapefile layer. I'm using this because I want to be able to set a filter on the shapefile layer and have it applied on several layers at once).
In this layer, I'm using categorized symbols.
The symbol is in fact a Geometry Generator, generating a polygon.

Now, whenever I go to Geometry Generator -> Fill -> Simple Fill and set draw effects, they're applied.
Same goes for just applying the draw effect on the Geometry Generator.

I save the project.
I reopen the project.
Draw filter is gone, whether I set it on the actual generator or on the fill.