Laser filling, covers too much

Alright, another topic, hopefully less of a basic PEBKAC issue now.
I’m trying to expose photosensitive PCB’s with an UV laser, so that’s quite fine. I keep tweaking the parameters and I’m getting better results, but I notice how the laser raster merge covers too much. This is getting in the way of fine PCB traces. The preview of the laser path matches the final result very well, however. The PCB file is in SVG.

I tried to increase overscan to 0,1 and 0,5mm but that doesn’t seem to make a difference.
Laserweb 4.0.998, grbl 1.1h